Browsing by Author "Leatherdale, Scott"

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A remotely delivered exercise-based rehabilitation program for patients with persistent chemotherapy-induced peripheral neuropathy (EX-CIPN): Protocol for a phase I feasibility trial
(Public Library of Science (PLOS), 2025) Antonen, Eric M.; Nadler, Michelle B.; Langelier, David M.; Campbell, Kristin L.; Flamer, David; Cho, Jang Hyuk; Capozza, Scott; Avery, Lisa; Bland, Kelcey A.; Leatherdale, Scott; Manthorne, Jackie; Jones, Jennifer M.
Background Chemotherapy-induced peripheral neurotoxicity (CIPN) is a prevalent adverse effect of chemotherapy agents that is estimated to be present in 2/3 of patients who receive neurotoxic chemotherapy. In 30-40% of these patients, CIPN signs and symptoms can persist for months or years post-treatment. Recent studies have supported exercise as a feasible and possibly effective intervention for CIPN; however, more rigorous studies are needed to confirm feasibility, estimate efficacy, and clarify risk. In response, we developed an innovative virtual exercise-based rehabilitation program (EX-CIPN) for cancer survivors with persistent CIPN. Methods This study is a phase I study conducted at the Princess Margaret Cancer Centre in cancer survivors with persistent CIPN, with a focus on feasibility, acceptability, and safety. A total of 40 patients aged 18 or older, with persistent CIPN at least 6 months after chemotherapy completion will be recruited and receive the EX-CIPN program. The EX-CIPN program is a 10-week virtual home-based intervention that includes an individualized exercise program supported with a mobile application (Physitrack), wearable technology (FitBit), and weekly virtual check-ins with an oncology exercise specialist. This primary outcome of feasibility will be assessed by examining accrual, retention, and adherence rates. Acceptability will be assessed through qualitative interviews. Safety events will be monitored and reported based on CTCAE v5. Secondary outcomes will be collected using questionnaires and physiological assessments at baseline (T1), after the intervention (T2), and 3-months after intervention (T3). Conclusion This phase I study will determine intervention feasibility, acceptability, and safety and will inform the planning for a future Phase II RCT with the EX-CIPN intervention.
Body Mass Index and Missing Data: Examining the Levels, Patterns, and Impacts of Missing Data in a Large Cohort Study of Canadian Youth
(University of Waterloo, 2022-12-19) Doggett, Amanda; Leatherdale, Scott
Missing data are generally unavoidable in survey-based research. Small amounts of random missingness may not pose significant problems; however, issues arise when data are missing in large proportions or when missingness follows a systematic pattern. Survey items that are tied to social desirability can be markedly impacted by non-response. Youth are a major target for survey-based research, with many cohort studies using surveys to monitor youth health and their health behaviours. Two common health-related measures that are often collected using self-reported surveys are height and weight, used to calculate body mass index (BMI). BMI is used as a proxy for body adiposity at the population level to identify individuals with overweight or obesity (OWOB). BMI is an important measure for research and population surveillance as it is a well-established predictor of future chronic disease. Among youth, OWOB trajectories tend to track into adulthood, and there is substantial literature exploring youth OWOB and associated factors. However, few existing studies have examined youth nonreporting of height and weight. Those studies which have examined nonreporting suggest that for youth, BMI tends to be missing in high proportions (exceeding missingness for other measures) and often follows a systematic pattern of missingness. There are several methods through which researchers can manage missing data. The most common approach is complete case analysis (CCA), whereby missing cases are deleted, and analyses are performed using only complete data. Due to the loss of information, CCA can introduce inefficiencies and bias into statistical results. Hence, in situations where data are missing systematically and in high proportions, CCA is not recommended. More sophisticated techniques, such as multiple imputation (MI), can yield unbiased and efficient estimates in these situations; however, they are not commonly leveraged in epidemiological studies. In fact, systematic reviews have suggested that information on missing data is typically not presented. This dissertation aimed to explore levels, patterns, and impacts of missing data among youth, specifically focusing on nonreporting of height, weight, and subsequently calculated BMI using data from a large youth-focused survey. This research leveraged data from 74,501 youth who participated in the 2018/19 wave of the COMPASS study. The COMPASS study is a survey-based cohort study among youth aged 12-19 years in Canada examining a variety of different aspects of health and health behaviours. Study 1 examined variables associated with missingness in BMI, height, and weight using model selection in three separate logistic regressions. Study 2 examined patterns, hierarchies, and subgroups of missing BMI, height, and weight data using classification and regression tree (CART) models. Finally, Study 3 compared the differences in findings between CCA and MI missing data approaches in the context of factors associated with youth BMI through linear mixed models. Study 1 found that nearly 1 in 3 youth in this sample were missing BMI data. Among those with missing BMI, 32\% did not report their weight, 20\% did not report their height, 36\% reported neither weight nor height, and 12\% were reduced to missing due to unrealistic values. A greater proportion of females were missing weight only, whereas a greater proportion of males were missing height only. Of all the youth-reported measures, BMI, height, and weight showed the highest degree of missingness. For both males and females, perceiving oneself as overweight was associated with a greater likelihood of BMI being missing. Indicators of poor diet and physical inactivity were also significantly associated with missing BMI. Taken together, results of Study 1 suggest that social desirability played a significant role in nonreporting patterns, and it is likely that those who have a higher BMI are less likely to report their height or weight. Study 2 identified that certain subgroups of youth (characterized by various health behaviours and indicators) were more likely to be missing BMI. Confirming findings from Study 1, patterns of systematic missingness in BMI were identified using CART models. Examining the identified subgroups highlighted that a combination of weight perception, low physical activity, poor academic performance, and poor mental health almost certainly lead to nonreporting. Study 2 also identified a hierarchy of importance for the variables related to missingness in BMI, height, and weight, providing more context to the associations observed in Study 1 and highlighting the utility of a CART approach to examine missing data. Studies 1 and 2 illustrated that in this sample, BMI missingness was highly prevalent and non-random. Using the findings from these two studies, Study 3 illustrated the bias that can occur when missing data are not managed appropriately. MI and CCA approaches produced contrasting results across sex-stratified models examining factors associated with youth BMI. These results illustrated how bias from deleting cases may impact findings and lead to considerably different research conclusions, highlighting the importance of thorough examination and appropriate handling of missing data. This dissertation fills an important gap in the research examining patterns and impacts of missingness in youth BMI, height, and weight. In this dissertation, missingness in youth BMI was found to be highly prevalent and followed a systematic pattern. Identified patterns indicated that nonreporting was likely influenced at least in part by social desirability, and that those with a higher BMI were less likely to report their height and/or weight. Subgroups of youth who had poorer outcomes for physical activity, school grades, and mental health were nearly guaranteed to be missing BMI. When carried forward into an analysis examining factors related to youth BMI, deleting the missing cases introduced bias into findings. This research highlights a great need for improved missing data reporting and handling within youth OWOB research. Similar cohort studies that collect youth height and weight through self-report measures should perform thorough examinations of missing data and choose appropriate methodologies to manage missingness. This research also suggests that researchers should exert caution when interpreting and utilizing results from studies where missing data are not well-reported.
Changes to Recreational Programming Within the School Environment and Student Physical Activity: A Longitudinal Examination from Year 2 to Year 3 of the COMPASS Study
(University of Waterloo, 2016-05-16) Stefanczyk, Jennifer; Leatherdale, Scott
Objective: This study examined the influence of changes to school recreational programming on the prevalence and likelihood of Ontario and Alberta secondary school students meeting the (i) Canadian Society for Exercise Physiology (CSEP) physical activity guideline and (ii) ≥60 minutes of daily moderate to vigorous physical activity (MVPA). Methods: Student- and school-level data was obtained using Year 2 and Year 3 COMPASS data. This longitudinal analysis assessed how changes to school recreational programming (including the addition, modification or removal of intramurals/non-competitive clubs) within 20 intervention schools influenced student physical activity (PA) levels compared to students who attended a school that made no PA practice changes (True Control Schools; n=43) or made other PA practice changes unrelated to school recreational programming (Other Practice Intervention (OPI) Schools; n=23). PA was measured using two outcome variables: achieving the CSEP guideline and achieving ≥60 minutes of daily MVPA. Descriptive statistics, ANOVA and hierarchical longitudinal analysis were conducted with relevant covariates controlled for within the models. Results: Significant differences were found in the prevalence of students meeting (i) the CSEP guideline, and (ii) ≥60 minutes of daily MVPA between Year 2 and Year 3 of the COMPASS study. In Year 2, 31.0% of students met the CSEP guideline and 47.8% achieved ≥60 minutes of daily MVPA. In Year 3, 28.5% of students met the CSEP guideline and 52.2% achieved ≥60 minutes of daily MVPA. There were no significant differences in the school-level prevalence of a student meeting the (i) CSEP or (ii) MVPA guideline in intervention schools as compared to control schools respectively. Students that attended School 9 were significantly less likely to meet the CSEP guideline after modifications were made to their school recreational programming in comparison to students who attended true control (RR=0.74) and OPI (RR=0.73) schools. Moreover, students that attended School 15 were significantly less likely to achieve ≥60 minutes of daily MVPA after modifications were made to their school recreational programming in comparison to students that attended true control (RR=0.71) and OPI (RR=0.71) schools. Students who are male, have weekly spending money of $21-100 or greater than $100, have 1-4 or greater than 5 active friends, are enrolled in physical education, participate in varsity sports or community sports were significantly more likely to meet the CSEP and MVPA guideline. Furthermore, students who began participating in school recreational programming in Year 3 and students who participated in both Year 2 and Year 3 had a significant increase in likelihood of obtaining (i) the CSEP guideline and (ii) ≥60 minutes of daily MVPA compared to students who did not participate in either year. Conclusion: Current school-based PA programming appears insufficient, as the majority of youth in the COMPASS study are not achieving the recommended amount of PA suggested in the Canadian PA guidelines. This study identified 20 school recreational programming interventions between Year 2 and Year 3 of the COMPASS study. Only two of the interventions were statistically significant, however they did not have the desired effect on student PA. Three school recreational programming interventions that appear promising for future school-based PA research are also discussed. Future research should explore how to improve and tailor specific school recreational options within different contextual settings and with populations at greater risk of inactivity.
Characterizing poly-substance use and its associations with anxiety and depression among a sample of Canadian high school students
(University of Waterloo, 2022-01-05) Williams, Gillian Claire; Leatherdale, Scott
In any given year, one in five Canadians experience mental illness. The majority of mental illnesses originate in adolescence or young adulthood. Many complex factors can contribute to this, including substance use. However, research does not accurately measure how students are using substances. Typically, researchers examine one substance at a time (e.g., alcohol, cannabis, or cigarettes) but 20% of youth use more than one, or poly-substance use. Poly-substance use is the concurrent use of more than one substance (e.g., alcohol, cannabis, or cigarettes) within a specified period (e.g., the past 30 days). To address this research gap, this thesis examined substance use classes among adolescents and how those classes were associated with anxiety and depression, both cross-sectionally and longitudinally. This research will help inform future surveillance, prevention, and treatment efforts for youth substance use and mental health. Recent evidence indicates that one in five Canadian students in grades 9 to 12 engage in poly-substance use. Common patterns of substance use among adolescents have been identified, including a low use or no use group comprising most adolescents, a single or dual substance use group, a moderate poly-substance use group, and finally a higher poly-substance use group. Longitudinal research indicates that adolescents typically maintain substance use patterns over time but if they make a change, adolescents are more likely to increase rather than to decrease the number of substances they use over time. There is limited study of poly-substance use among Canadian youth and few studies have examined the role of recent increases in e-cigarette use among adolescents in poly-substance use over time. Poly-substance use has been associated with elevated symptoms of depression and anxiety among adolescents in cross-sectional research. Previous longitudinal research has identified mixed results. Additionally, previous longitudinal studies have not explored sex differences, despite known differences being identified in cross-sectional research and the knowledge that patterns of poly-substance use, anxiety, and depression are known to differ between female and male adolescents. The overall objective of this dissertation was to characterize poly-substance use and examine its associations with anxiety and depression among a sample of Canadian adolescents both cross-sectionally and longitudinally, stratified by sex. Specific objectives were to (1) determine the cross-sectional substance use classes among a sample of Canadian secondary school students and examine their associations with anxiety and depression symptoms, (2) examine the longitudinal bi-directional associations between poly-substance use and anxiety and depression among secondary school students over time and, (3) examine the longitudinal associations between latent classes of substance use and anxiety and depression scores over time among youth who use substances. This thesis made use of data from 3 waves of the COMPASS study (Wave 1: 2017/18, Wave 2: 2018/19, and Wave 3: 2019/20). Students reported their substance use (alcohol, cannabis, cigarettes, and e-cigarettes) and anxiety and depression symptoms at each wave. The first manuscript made use of cross-sectional data (Wave 1: 2017/18) while the second two used longitudinal linked data from all three years (Wave 1: 2017/18, Wave 2: 2018/19, and Wave 3: 2019/20). The first manuscript examined cross-sectional patterns of substance use among a sample of Canadian secondary school students and their associations with clinically relevant symptoms of anxiety and depression, or both in the 2017/18 school year. Results identified three classes of substance use: poly-use, dual use, and non-use. These results indicate that Canadian secondary school students are engaging in dual and poly-substance use. Those with anxiety, depression, or both had higher odds of being in the poly-use class compared to the non-use class. Symptomology was also associated with belonging to the dual use class except among males with anxiety symptoms only. After identifying a cross-sectional association, the second manuscript used data from students linked over three years to examine the directionality of the association. The objective was to examine the bi-directional associations between (1) number of substances used and anxiety and depression among all students and (2) poly- versus single substance use and anxiety and depression among students who used substances. Among all male students, a uni-directional association was identified where an increase in the number of substances used was associated with reduced anxiety symptoms between Waves 1 and 2. Among students who used substances, uni-directional associations were identified between Waves 2 and 3 where poly-substance use was associated with increased depression among males and increased anxiety among females and males. Finally, given that the previous manuscript provided evidence that poly-substance use preceded changes in anxiety and depression symptoms among students who used substances, the focus of the final manuscript was on this direction of effect. The third manuscript examined the longitudinal associations between latent classes of substance use over time and anxiety and depression scores among youth who used substances. These analyses identified three classes of substance use over time: occasional alcohol and e-cigarette use, escalating poly-substance use, and consistent poly-substance use. After controlling for relevant covariates, consistent poly-substance use was associated with depression but not anxiety. Additionally, escalating poly-substance use was associated with depression among male students. This dissertation fills an important gap with respect to our knowledge of poly-substance use and its association with anxiety and depression among adolescents in Canada. The findings highlight the need to consider adolescent poly-substance use and have implications for practice and research. Given that many students reported poly-substance use, surveillance and prevention strategies should consider substance use patterns, including dual and poly-substance use. As this research identified substance use as a potentially modifiable behaviour associated with adolescent mental health, it may also be useful to consider a mental health component in substance use programming. Future research examining this association should additionally consider simultaneous poly-substance use, clinical measures of anxiety and depression, and capture reasons for substance use to further strengthen and understand the association between poly-substance use and anxiety and depression among adolescents.
Evaluating the Impact of Changes in School-Based Tobacco Interventions Among Never Smokers Between Year 2 and Year 3 of the COMPASS Study
(University of Waterloo, 2016-07-07) Aleyan, Sarah; Leatherdale, Scott
Objective:To examine how changes in school-based tobacco programming within a school influenced smoking susceptibility and smoking initiation outcomes among a sample of grade 9 to 12 students over time. Methods: This study used longitudinal data from Year 2 and Year 3 of the COMPASS study. The study used school-level data from 79 schools within Ontario using the School Policies and Practices (SPP) questionnaire as well as student-level data on 14965 grade 9 to 12 students who were never smoker individuals at baseline (Year 2) using the COMPASS questionnaire (Cq). This study did not examine individuals who were tried smokers at baseline. Binary logistic regression models were used to examine the impact of changes in tobacco programming within a school had on the relative risk of students’ reverting in smoking susceptibility status, becoming susceptible to smoking or initiating smoking behaviour in Year 3. Results: Between Year 2 and Year 3 of the study,22 schools (out of 79) Ontario schools reported implementing a new tobacco intervention in their school. Out of 22 schools, one school intervention had the desired impact of significantly increasing the likelihood of a susceptible never smoker individual at baseline reverting in smoking susceptibility that corresponded with a reduced risk of smoking initiation. One intervention significantly decreased the likelihood of individuals trying smoking, however these promising effects were only observed among the sample of non-susceptible never smoker individuals at baseline. In contrast, two interventions had the undesirable impact of significantly increasing the likelihood of a student initiating smoking behaviour among non-susceptible never smokers at baseline. Conclusion: The evidence presented here indicates that the majority of school-based tobacco prevention programming do not show promise in reducing adolescent smoking susceptibility and initiation among never smokers. Progress in preventing smoking initiation among never smoker youth will require coordinated and comprehensive efforts from various stakeholders. In addition, there is a need for innovative methods to be used in determining which interventions work, for which target audience, and in what context to guide the formulation of tailored and effective programming.
Evaluating the Impact of Changes to School-Level Alcohol Prevention Policies and Programs on Youth Binge Drinking: A Longitudinal Analysis of the Year 2 and Year 3 Data of the COMPASS Study
(University of Waterloo, 2016-06-15) Herciu-Ivascu, Alin Cezar; Leatherdale, Scott; Chaurasia, Ashok; Hammond, David
Objective: The purpose of this study was to investigate the effectiveness of alcohol prevention policies and programs implemented in a linked sample of Ontario COMPASS high schools in reducing youth binge drinking over time at both the population- and individual–levels. Methods: This longitudinal study utilized the COMPASS Year 2 and 3 student- and school–level data obtained from the 16,491 linked students who had complete information for the binge drinking outcome measure as well as the relevant student-level covariates and who attended the same 77 Ontario high schools in both years. The COMPASS student-level questionnaire (Cq) was used to measure the relative student-level covariates as well as the binge drinking outcome measure. Binge drinking was measured using the question: “In the last 12 months, how often did you have 5 drinks of alcohol or more on one occasion?” Students who indicated that they consumed 5 or more alcoholic drinks in one occasion either once a month or more frequently were classified as being current binge drinkers. Conversely, individuals who responded that they engaged in a similar pattern of alcohol consumption ranging from less than once a month to never were labelled as being non-current binge drinkers. School-level data regarding the changes in alcohol prevention policies and programs that occurred from Year 2 to Year 3 for this sample of schools was assessed using the Year 3 COMPASS School Policies and Practices (SPP) administrator questionnaire. Using this linked sample, a McNemar’s test was performed to see if there was any significant change in the prevalence of student binge drinking from Year 2 to Year 3. Difference-in-differences changes analyzed using a One-Way Analysis of Variance (ANOVA) and a longitudinal model analyzed using a Generalized Estimating Equation (GEE) were used to determine if changes in school-level alcohol prevention interventions between these two years were significantly associated with a change in the school-level prevalence of student binge drinking as well as with a change in individual student binge drinking behaviours, respectively, over time. Results: At the population level, neither of the 19 specific alcohol prevention interventions (F = 1.00, df1 = 19, df2 = 3679, p-value = 0.4631) nor any of the 6 distinct intervention categories (F = 1.18, df1 = 6, df2 = 1553, p-value = 0.3123) were associated with a statistically significant relative reduction in the school-level prevalence of binge drinking from Year 2 to Year 3 when compared to the change observed in the pooled sample of control schools. Similarly, neither of the 19 specific alcohol prevention interventions (p-value = 0.6976) nor any of the 6 distinct intervention categories (p-value = 0.5355) were associated with a statistically significant increase or decrease in an average student’s risk of being a current binge drinker from Year 2 to Year 3 who attended an intervention school (or category) in comparison to the risk of a similar average student who attended one of the control schools while controlling for important student- and school-level covariates. As expected, the McNemar’s test showed that the proportion of current binge drinkers in the linked sample increased significantly over time as the cohort aged from 14.9% in Year 2 to 24.4% in Year 3 (p-value <.0001). Implications and Conclusions: Only 19 of the 77 Ontario high schools implemented new school-level alcohol prevention interventions between Year 2 and Year 3 with none of them being associated with a statistically significant decrease in binge drinking at the population or the individual level. However, a zero tolerance punishment policy and a student education program involving displays and pamphlets may have shown some potential for possibly having some public health impact on this behaviour at the individual level and should be further explored. Overall, the high school setting may not be the best place to intervene for this type of work and/or the current school-level alcohol prevention initiatives implemented in this province may be too simplistic in nature. Future research should evaluate the impact of more intricate programs that are only partially implemented within the high school environment as well as higher macro-level policies like increasing taxation on alcohol, increasing the minimum legal drinking age, and banning alcohol advertisements within Ontario as these may serve as more promising approaches for reducing youth binge drinking in this province. All of this is important since, unsurprisingly, the prevalence of binge drinking in this sample increased significantly over time as students aged. All in all, this is the first quasi-experimental longitudinal study to simultaneously evaluate the potential ability of multiple different high school-level alcohol prevention interventions to possibly reduce youth binge drinking in order to generate real-world evidence about this topic in Ontario.
Evaluating the impact of participation in school-based physical education lessons on adolescent health and wellbeing in Ontario: Findings from the COMPASS study
(University of Waterloo, 2025-01-30) Buchan, Marisa Claire; Leatherdale, Scott
Physical activity rates among adolescents in Canada are critically low; only about one in every three grade 9 students are meeting the recommended 60 minutes per day of moderate to vigorous physical activity (MVPA). These high rates of physical inactivity among youth are alarming, as physical activity is essential for both physical and mental wellbeing, and it sets the foundation for healthy habits in adulthood. School-based physical activities including physical education (PE) classes, and intramural and varsity sport programs are ideally situated for the promotion of physical activity as they can reach a large number of youth and overcome many of the barriers associated with extracurricular activities. PE is designed to provide opportunity for youth of all ages to engage in physical activity that is structured into their weekly routine. However, in secondary school, a period that is critical for establishing healthy behaviour patterns for later in life, PE becomes non-mandatory for students in many provinces and territories across Canada, resulting in a missed opportunity to engage adolescents in regular physical activity. Ontario currently has the most lenient PE policy in Canada, with students only required to complete one secondary school-level PE course. To date, only four studies have examined the impact of PE programming in Canada on physical activity levels, only one of which included students from the province of Ontario. No published studies to date have explored the impact of PE participation on mental health outcomes among adolescents in Canada. The lack of evidence in this domain renders it challenging to determine the effectiveness of PE or make recommendations to enhance PE programs to maximize their impact on student health and wellbeing. This dissertation aimed to provide a deeper understanding of the patterns of physical activity behaviours and the impacts of participating in non-mandatory secondary school PE on physical activity and mental health outcomes among adolescents in Ontario. Specifically, Study 1 characterized longitudinal physical activity profiles of non-mandatory PE participation, adherence to physical activity guidelines, and sport participation throughout secondary school. Study 2 quantified the impact of participation in PE on physical activity levels, over time. Study 3 quantified the impact of PE participation on student mental health, over time. This dissertation utilized linked longitudinal data from students in Ontario who participated in four consecutive years of the COMPASS Study (Time 1: 2015-16; Time 2: 2016-17; Time 3: 2017-18; Time 4: 2018-19). The COMPASS Study is a school-based prospective cohort study (2012-2027) that collects demographic, behavioural, and mental health data from students annually across Canada. Study 1 utilized a repeated measures latent class analysis to identify longitudinal physical activity profiles of adolescents in Ontario. Studies 2 and 3 utilized linear mixed models to estimate the average effect of PE participation on (a) minutes of MVPA (Study 2) and (b) symptoms of anxiety, (c) symptoms of depression, and (d) psychological wellbeing (Study 3), over time. Models in Studies 2 and 3 were adjusted using doubly robust propensity score methodology to account for self-selection biases that may influence PE participation. Findings from Study 1 illustrated that there are distinct, clustered physical activity profiles among adolescents which vary by sex; three physical activity profiles were identified among both female and male students: Guidelines, PE & Sports, and Guidelines & Sports. A fourth profile was identified among male students only: Inactive. Study 2 demonstrated that participation in secondary school PE had a significant positive impact on MVPA levels over time, and effects were most pronounced for male students and during the semester of PE participation. Study 2 also illustrated that the benefits of PE remained present in the semester opposite to PE participation, suggesting that the benefits of PE extended beyond the MVPA accumulated during class-time. In Study 3, PE participation was not associated with symptoms of anxiety or depression, over time. Study 3 also found that male students enrolled (but not currently participating) in PE were found to have higher psychological wellbeing compared to those not enrolled in PE within the academic year. This dissertation fills an important gap with respect to our understanding of PE programming in Ontario secondary schools. Findings from this dissertation revealed that many students are choosing not to enroll in PE, with a particularly high-risk subgroup of male adolescents showing low participation across several physical activity behaviours during secondary school. Among male students who elect to participate, PE was found to positively impact time spent in MVPA and psychological wellbeing. These results highlight the potential of PE for improving the health and wellbeing of adolescents, although low participation rates limit these benefits being experienced at the population-level. Importantly, all three studies identified sex-based differences in the physical activity profiles and the impact of PE on health outcomes; female students were found to have lower PE participation rates and experienced reduced benefits compared to male students. These result underscore the importance of promoting inclusive environments in PE to ensure health benefits are experienced by all adolescents, regardless of sex and other key characteristics. Findings from this dissertation offer valuable insights for public health programming, particularly within the school context; decision-makers in Canada should explore ways to increase PE participation across secondary schools, paying particular attention to female students and those not participating in other forms of physical activity.
Examining how changes in school-level intramurals impact physical activity among Ontario youth over time: A natural experiment evaluation from the COMPASS study
(University of Waterloo, 2021-06-21) Burns, Kathleen Elizabeth; Leatherdale, Scott
Introduction: Moderate-to-vigorous physical activity (MVPA) has many health benefits for youth. However, the majority of Canadian youth are falling short of the recommended 60 minutes of MVPA per day. Since youth spend a large proportion of time in school, regardless of socio-economic status, and evidence shows that characteristics of the school environment can influence youth MVPA, schools represent an equitable and effective setting for providing physical activity programming to youth. Intramurals are one example of inclusive school-based physical activity programs given they tend to be accessible, affordable, and less competitive compared to other school-based physical activity programs (e.g., varsity sports). Intramurals address common barriers to youth sport participation and MVPA, and are positively associated with these outcomes, however, there is limited evidence examining if offering intramurals is protective against the declining trajectory of youth MVPA. Despite this lack of evidence to inform intramural offerings, schools continue to add and remove intramurals each year as part of their real-world practice actions to promote activity among students. This research aimed to generate novel practice-based evidence on the effect of intramural offerings by using a quasi-experimental design to evaluate if changes in the number of intramurals associate with youth MVPA over time. More specifically, Study 1 examined how general changes (added, removed, no change) in intramurals were associated with youth MVPA over time, Study 2 examined how changes in the type (team and individual) of intramurals were associated with youth MVPA over time, and Study 3 examined how changes in gender-specific (female-, male-only) and co-ed intramurals were associated with youth MVPA over time. Methods: This dissertation used three years of longitudinal school- and student-level data from Ontario schools participating in year 5 (Y5: 2016-2017), year 6 (Y6: 2017-2018) and year 7 (Y7: 2018-2019) of the COMPASS study. School-level covariates and intramural data from 55 schools in Ontario, Canada were obtained from the School Programs and Policies (SPP) Questionnaire in Y5 and Y6. Baseline demographics and data on sport participation and MVPA were measured by the student COMPASS Questionnaire (Cq) in Y5, Y6 and Y7 on a sample of 4417 students. A longitudinal quasi-experimental study design was employed, as data on the outcome were measured at pre-intervention (Y5), intervention (Y6) and post-intervention (Y7) time points and were compared between non-randomized intervention and control groups. Hierarchical linear mixed regression models were used to examine if changes in intramurals in Y5 to Y6 were associated with MVPA over time separately for males and females. A novel modeling approach to program evaluation was utilized to create indicator variables representing the yearly intramural changes: (i) intramural changes in year 6 and (ii) intramural changes in year 7 for each study. These indicator variables were included in the models and allowed for the assessment of their effect at those respective years. Results: Intramural participation was positively associated with youth MVPA over time and youth MVPA decreased over the three-year study period. In Study 1, general changes in intramurals (added, removed, no change) were not associated with youth MVPA over time. In Study 2, adding team and individual intramurals was significantly and positively associated with female MVPA in Y6, regardless of intramural participation. In Study 3, gender-specific and co-ed intramurals were not associated with youth MVPA over time, however the association between adding gender-specific intramurals and female MVPA should be further explored, as the p-value of this association was at the level of significance (α=0.05). Discussion: The novel findings from this research address important gaps in the literature on intramurals and physical activity, and contribute to our understanding of how real-world changes in school-level intramurals impact the MVPA of students within these schools over time. In Study 2, we found that adding team and individual intramurals was positively and significantly associated with female MVPA in Y6, regardless of participation. This suggests an indirect association between changes in intramurals at the school-level and individual female student MVPA in those schools. This may be explained by the fact that adding a variety of intramurals creates a supportive and inclusive physical activity environment for females, by targeting female motivations for physical activity (e.g., peer socialization, inclusion and keeping fit) and important intra- and interpersonal factors for female physical activity (e.g., autonomy and self-efficacy). In Study 3, the association between adding gender-specific intramurals and female MVPA was positive, but non-significant. Gender-specific intramurals may promote a supportive physical activity environment and encourage physical activity by fostering self-efficacy, enjoyment and peer support, especially among females. This association should be examined with a larger school sample, as this analysis may have been under-powered at the school-level. Based on Study 1, 2 and 3, changes in intramurals were not significantly associated with male MVPA over time. This suggests that changes in intramurals are not effective at increasing MVPA among males, and may be explained by the fact that the inclusive and supportive nature of intramurals generally do not target male motivations for physical activity, which include competition, strength and winning. Although changes in intramurals were generally not associated with youth MVPA, intramurals are associated with several other important outcomes among youth, such as sport sampling, physical literacy, socialization, school connectedness and reduced substance use. Schools should offer intramurals as inclusive physical activity programs, in addition to other physical activity programs and policies, to encourage equitable access to sport and physical activity and to foster healthy behaviours among youth.
Examining the Role of the School Food Environment in Moderating Sugar-sweetened Beverage Consumption Among Adolescents in Alberta and Ontario, Canada: Cross-sectional and Longitudinal Evidence from the COMPASS Study
(University of Waterloo, 2018-04-27) Godin, Katelyn Marina; Leatherdale, Scott
Adolescents represent the greatest consumers of sugar-sweetened beverages (SSBs) in Canada, which is concerning, given the numerous adverse health outcomes associated with frequent SSB intake. Provincial school nutrition policies represent one population-level strategy intended to promote healthy dietary choices among Canadian youth. Both the Alberta Nutrition Guidelines for Children and Youth (ANGCY) and Ontario’s Policy/program Memorandum no. 150 (P/PM 150) recommend restrictions in SSB availability in school food outlets (e.g., cafeterias, vending machines, etc.) to decrease students’ access to products. There exists a broad range of contextual factors outside of schools that influence youths’ dietary choices; influences within other environments (e.g., the home, community, and larger regulatory contexts) can support or undermine school-based interventions, and should be accounted for in the development and evaluation of these initiatives. This dissertation research used the socioecological model as a theoretical framework to examine the role of the school context in influencing Canadian adolescents’ SSB intake in Alberta and Ontario. The objectives were to (i) characterize Canadian adolescents’ SSB consumption patterns; (ii) describe school food environment characteristics in Canadian secondary schools; (iii) describe how these characteristics reflect school-level compliance with provincial school nutrition policies; (iv) identify associations between school food environment characteristics and measures of students’ SSB intake; and, (v) identify potentially promising contexts and/or strategies for future population-level initiatives to reduce adolescents’ SSB intake. Three manuscripts served these objectives using student- and school-level data from the COMPASS study. The first two manuscripts represent cross-sectional analyses (2013/14), while the third manuscript includes longitudinal analyses (2013/14 to 2015/16). The first manuscript examined how several food purchasing behaviors (i.e., sources of meals/snacks) within and outside of the school context are associated with adolescents’ SSB consumption, and whether these associations vary by province. This study identified that most of the food purchasing behaviours were significantly and positively associated with greater rates of SSB consumption. Meal/snack purchases on weekends (versus weekdays) and from food outlets off-school property (versus on-school property) had a greater association with SSB consumption. The research identified a significantly higher rate of SSB intake among Albertan participants and a number of interesting interaction effects between province and various food purchasing behaviours, providing evidence that students’ rate of SSB intake may be related to differences in provincial school nutrition policies. The second manuscript provided a scoping assessment of several characteristics of the secondary school food environment (i.e., comprising features of the school and school neighbourhood) in Alberta and Ontario, provincial differences across these school characteristics, as well as whether these characteristics are associated with students’ SSB consumption rate. This study identified that participants had access to several potential sources of SSBs during their time in school; most schools were within walking distance of one or more external food outlets and a considerable proportion of schools stocked various types of SSBs in their vending machines. SSBs were significantly less available in Ontario schools’ vending machines compared to those in Alberta, suggesting that P/PM 150 is more effective than the ANGCY at restricting SSB availability in school vending machines. Few of the school food environment characteristics assessed were significantly associated with students’ SSB intake. The third manuscript examined changes in product availability within secondary schools’ beverage vending machines, changes in students’ weekday intake of SSBs over time, and the associations between these measures of beverage availability and SSB intake. Schools were separated into three policy groups: ‘Alberta’; ‘Ontario public schools’; and, ‘Ontario private schools’. Most SSB types examined were least available in Ontario public schools’ vending machines across all time points. Generally, vending machine beverage availability did not vary significantly over time. Across all policy groups, participants’ rate of soft drinks consumption decreased as they progressed through secondary school, while their intake of sweetened coffees/teas increased; other SSB outcome measures remained fairly stable. Students in Alberta reported the greatest frequency of SSBs intake across all time points and measures. There was limited evidence that changes in vending machine beverage availability was significantly associated with students’ SSB consumption. This dissertation enhances our current understanding of Canadian adolescents’ SSB intake patterns, the Canadian secondary school food environment, and the successes and shortcomings of school nutrition policies. This work signals the need for continued efforts to reduce adolescents’ SSB intake. This dissertation illustrates that the school food environment represents a source of SSBs for Canadian adolescents, since most schools are nearby external food outlets and many schools have SSBs available for sale within school vending machines. However, this research highlights that schools are one of many contexts that influences adolescents’ dietary behaviours, and efforts to limit the in-school availability of SSBs in vending machines have a limited impact on measures of adolescents’ SSB intake. This research signals the need for school-based interventions to be supported by parallel population-level initiatives that encourage healthy dietary choices among Canadians.
Examining trends, predictors, and mediators of e-cigarette use and smoking among Canadian youth: Findings from the COMPASS study
(University of Waterloo, 2021-04-19) Aleyan, Sarah; Leatherdale, Scott
Abstract The objectives of this dissertation were to (1) examine trends and predictors of youth e-cigarette use and cigarette smoking, (2) explore potential mediators of the association between initial e-cigarette use and cigarette smoking uptake, and (3) evaluate the impact of Ontario’s introduction of e-cigarette minimum legal sales age (MLSA) laws on youth e-cigarette use. The study objectives were explored in three separate manuscripts using data gathered from a sample of students in two Canadian provinces, Ontario and Alberta, that participated in a school-based study (COMPASS). Using longitudinal data from students in Ontario and Alberta, the first manuscript examined changes in the prevalence of exclusive e-cigarette use, exclusive smoking and dual use of e-cigarettes and cigarettes over time. This manuscript also examined how frequency of e-cigarette use and smoking (i.e., number of days used in the past month) predicted exclusive e-cigarette use, exclusive cigarette smoking and dual use of both products after a one- and two-year follow-up period. Study findings showed an increase in all usage categories over time. Findings also demonstrated some differences in predictors of exclusive e-cigarette use, exclusive smoking and dual use. For instance, frequent e-cigarette use (i.e., use for 4 or more days in past month) was not a significant predictor of exclusive smoking at either follow-up time point, but did predict dual use at both the one- and two-year follow-up. Notably, findings also showed that students who reduced their frequency of e-cigarette use were less likely to report being exclusive e-cigarette users and dual users at the two-year follow-up. The second manuscript investigated whether having one or more smoking friends mediated the association between initial e-cigarette use and cigarette smoking onset among a longitudinal sample of youth who were never smokers at baseline. Longitudinal findings showed that having one or more smoking friends did not mediate the association between e-cigarette use and subsequent cigarette smoking. Similarly, longitudinal results showed that having smoking friends did not mediate the association between e-cigarette use and subsequent dual use of e-cigarettes and cigarettes. Rather, our study findings indicated that smoking friends significantly predicted both e-cigarette use and cigarette smoking among youth. The third manuscript evaluated the influence of an e-cigarette law introduced in Ontario using a quasi-experimental design. In January 2016, Ontario implemented a law restricting the sale of e-cigarettes to those 19 and over. At that time, Alberta did not have a similar law in effect. Using a repeat cross-sectional sample, we examined the impact of Ontario’s law on the school-level prevalence of e-cigarette use among a sample of Ontario schools versus Alberta schools. Furthermore, using a longitudinal sample of students, we evaluated the impact of this law on the individual likelihood of e-cigarette use among students in Ontario versus Alberta schools. Findings based on the repeat cross-sectional sample showed that the changes in the average school-level prevalence of e-cigarette use within the Ontario sample were not significantly different from the changes seen in the Alberta sample. Findings based on the longitudinal sample showed increases in e-cigarette use over time among students in Ontario and Alberta. However, the increase observed among students in Alberta (i.e., where no e-cigarette MLSA law was implemented) was larger than the increase seen among students in Ontario (i.e., where an e-cigarette MLSA law was implemented). The studies examined within this dissertation project contribute towards our understanding of e-cigarette use and cigarette smoking among Canadian youth. Longitudinal findings indicated that having one of more smoking friends is a common risk factor that is associated with both e-cigarette use and cigarette smoking among youth. These findings suggest that the role of peers should be considered within the design of youth-based prevention interventions. Longitudinal findings showed an increase in e-cigarette use over time among youth in our study sample. Longitudinal findings also indicated that Ontario’s introduction of e-cigarette MLSA laws had an impact in attenuating these increases in e-cigarette use, but did not reverse the overall increasing trend in use among youth in our sample. Collectively, our study findings suggest the need for a more comprehensive approach to address the rise in e-cigarette use among Canadian youth.
Exploring reluctancy towards help-seeking at school among youth in the COMPASS study
(University of Waterloo, 2020-07-06) Doan, Natalie; Leatherdale, Scott
Background: Despite the high prevalence of mental health problems that emerge during adolescence, it has been observed that young people are among the least likely to seek help. Considering that many adolescents spend most of their weekday waking hours at school, the school system has the potential to support positive mental health behaviours in students. Objectives: The goal of this thesis was to identify the student and school characteristics associated with a reluctancy towards help-seeking for mental health concerns at school. Specifically, the objectives of this study were to: (1) estimate the proportion of students reporting reluctance towards help-seeking at school; (2) identify the student and school characteristics associated with reporting reluctance towards help-seeking at school; and (3) examine whether social support moderates the relationships between the availability of school mental health professionals and services and help-seeking reluctance. Methods: Data from the 2018-2019 wave of the COMPASS study was examined. In total, 47,290 Grade 9 to 12 students attending 116 schools were included in the final analyses. GEE models were used to assess the student and school characteristics associated with attitudes towards help-seeking for mental health concerns at school. Results: Over half (58%) of students reported being reluctant towards help-seeking at school. Schools in a rural/small urban area had students reporting reluctancy towards help-seeking at a lower odds than medium/large urban schools (aOR = 0.85, 95% CI = 0.79, 0.93). When compared to schools in an area where the median household income was between $50,000-75,000, schools with a median income between $75,000-100,000 were at greater odds of students reporting reluctancy towards help-seeking (aOR = 1.20, 95% CI = 1,01, 1.43). Students who reported poorer mental health as indicated by self-rated mental health (aOR = 1.76, 95% CI = 1.65, 1.87), emotion regulation (aOR = 1.08, 95% CI = 1.07, 1.09), and flourishing (aOR = 0.96, 95% CI = 0.96, 0.97), family (aOR = 2.31, 95% CI = 2.16, 2.47), and peer support (aOR = 1.20, 95% CI = 1.13, 1.31), and school connectedness (aOR = 0.93, 95% CI = 0.92, 0.93) were at greater odds of being reluctant towards help-seeking at school than students who reported more favourable scores on these variables. The non-significant relationships between the availability of mental health professionals and services with help-seeking attitudes were not modified by social support. Conclusion: Many students reported being reluctant towards help-seeking at school. Few school and many student characteristics were associated with help-seeking attitudes at school among youth. This research provides important direction for future help-seeking interventions especially those targeting priority student populations. It is vital to further examine how school mental health strategies can be used to promote positive help-seeking attitudes among students.
Exploring the association between cannabis use, depression, anxiety and flourishing in youth: a cross-sectional analysis from year 5 of the COMPASS Mental Health pilot data
(University of Waterloo, 2018-04-30) Butler, Alexandra; Leatherdale, Scott
Cannabis use and mental health problems are highly prevalent among Canadian youth. While repercussions associated with cannabis are ubiquitous throughout the population, youth are at an increased risk as the brain is exceptionally susceptible to adverse effects during this stage of development. Youth are at a disproportionate risk for addiction, developing a cannabis use disorder, depression, anxiety and psychosis. Moreover, the risk of developing a substance use problem is doubled in people with mental illness compared to the general population, whereby at least 20% of people with a mental illness have a co-existing substance use problem. Gaps remain within the literature that explore how the effects of positive wellbeing, in the presence or absence of mental illness, can serve as a protective measure against cannabis use. The objective of my thesis was to examine if depression or anxiety were associated with youth cannabis use; and investigate whether flourishing moderates these associations. My approach was guided by the differential susceptibility framework and used a cross-sectional analysis of the mental health module pilot data collected in year 5 (Y5[2016-2017]) of the COMPASS study. Data from 8,179 grades 9-12 students were collected from 10 secondary schools in Ontario and British Columbia, Canada. Participants were included based on a complete case analysis for a total of 8,040 students being eligible participants. Self-report questionnaires were used to assess symptoms of depression [CESD-R-10], anxiety [GAD-7], flourishing [Deiner’s Flourishing Scale] and cannabis consumption using measures that assess cannabis ever use and frequency of use. Logistic regression analysis (binary and ordinal) and product-term interactions were used to examine the associations between mental health and youth cannabis use, and the potential moderating effect(s) of flourishing. In my sample, 33% of participants had ever used cannabis, 51% and 38% reported elevated depressive and anxiety symptoms, respectively. Associations between depression, anxiety, and cannabis use were no longer significant when flourishing was added to the models. In addition, there was no evidence suggesting a moderating effect of flourishing as all interactions were not statistically significant. Instead, robust associations were found between flourishing and cannabis use. Indicators of mental wellbeing, such as flourishing, appear to be associated with a lower likelihood of cannabis use, even after controlling for depression and anxiety. Results suggest prevention strategies for youth cannabis use should aim to foster mental wellbeing among all youth, rather than exclusively targeting those experiencing mental health problems. Future longitudinal studies should test the sequential relationship between cannabis use and changes in both positive and negative mental health.
A longitudinal examination of the associations between cannabis use, physical activity, and CSEP guideline achievement among youth in the COMPASS study
(University of Waterloo, 2020-12-15) Watorowski, Christopher; Leatherdale, Scott
Background: There is a lack of conclusive longitudinal literature regarding cannabis use frequency and physical activity in Canadian youth. While it is documented that rates of physical activity are decreasing and cannabis use in Canadian youth is among the highest in the world, the strength and direction of this longitudinal association is contradictory. Objectives: This thesis will examine the relationship between cannabis use and physical activity through two main objectives: 1) Are the changes in cannabis use frequency over time associated with the relative change in MVPA? 2) Are the changes in cannabis use frequency over time associated with the likelihood of meeting the CSEP PA guidelines at two-year follow-up? Methods: Data from years 5 (2016-17), 6 (2017-18), and 7 (2018-19) of the COMPASS study were used. Overall, 7400 Grade 9 to 12 students attending 75 schools were included in the analyses. Linear mixed regression models and generalized estimating equations were used to longitudinally examine the associations between student-level characteristics and cannabis use on the relative change in MVPA and the likelihood of meeting the CSEP guidelines, respectively. Results: Less than a third (28%) of youth reported achieving the CSEP guidelines at baseline, with the average MVPA decreasing by approximately 12% from baseline to two-year follow-up. Cannabis use in youth also increased from approximately 8% to approximately 31% by two-year follow-up. However, it was found that neither the increase nor the decrease in cannabis use was associated with either relative changes in MVPA or CSEP guideline achievement at two-year follow-up. A decrease in relative MVPA was seen for students who reported being underweight (β= -14.4 (SE=6.48)), and had met the CSEP guidelines at baseline (β= -56.6 (SE=4.65)), where an increase in relative MVPA was seen for those who were in grade 11 (β= 47.7 (SE=17.81)). Youth who were males (aOR=2.07, 95% CI = 1.83, 2.34), current binge drinkers (aOR=1.35, 95% CI = 1.09, 1.69), and met the guidelines at baseline (aOR=3.59, 95% CI = 3.16, 4.09) had higher odds of meeting the CSEP guidelines at two-year follow-up. Students who were non-white (aOR=0.86, 95% CI = 0.75, 0.98), were underweight (aOR = 0.82, 95% CI = 0.68, 0.98) or had not stated weight status (aOR = 0.63, 95% CI = 0.55, 0.72) were of lower odds of meeting the CSEP guidelines at two-year follow-up. The interaction between cannabis use and CSEP achievement at baseline was not significantly associated with CSEP achievement at two-year follow-up. Conclusion: Few student-level characteristics were associated with CSEP guideline achievement and relative MVPA in youth. However, this research provides a valuable understanding to this longitudinal association with cannabis use and other student-level characteristics. Using this research, future initiatives can better prioritize the needs of at-risk student populations. Future research should continue to investigate this complex relationship longitudinally in attempt to promote youth health and mitigate harmful health behaviours.
Machine Learning Approach and Adolescent Health Implementation of Machine Learning Algorithms to Explore Adolescent Health, BMI and Weight Perception Using COMPASS Study
(University of Waterloo, 2024-09-24) Zhang, Qianyu; Leatherdale, Scott; Chen, Helen
Abstract Introduction Adolescence is critical for behaviour formation and physical, social, and psychological changes. The risk related to unhealthy behaviours occurring during this stage can emerge in early adulthood and could lead to adverse outcomes. The COVID-19 pandemic has significantly impacted the youth’s characteristics and the school’s learning environment. Exploring the profile of Canadian youth before and after COVID-19 helps understand the factors that influence student engagement in the multi-domain setting, including school activities, mental health, healthy eating, etc. Among the various aspects of student profile, childhood obesity and weight perceptions are two important topics for Canadian youth's health and well-being. Obesity in children is a complex public health concern in Canada. Almost 1 in 7 children are considered obese, and 75% of obese children are obese in their adulthood when they grow up. Additionally, a youth’s perception of their weight is often connected to their BMI status. Studies have shown that adolescents who are overweight and obese tend to underestimate their true weight, and the ones with normal weight could overestimate their weight status. Both overweight and obese or misperception of body weight are risk factors for developing non-communicable diseases in adulthood and can lead to worse mental health issues, such as lower self-esteem. Therefore, observing these two aspects and related impactful factors is necessary for informing youth obesity preventive intervention. Compared to traditional statistics, machine learning has proven effective in handling the complex relationships between multidomain variables and in detecting nonlinear relationships between the predictor variables and the target outcome. This thesis explores behavioural patterns, specifically BMI and weight perception, among the Canadian youth participating in the COMPASS study. Objective and Methods The dissertation utilized Wave 7 (2018-19) and Wave 9 (2020-21), and linked data from Wave 9 to 11 (2020-23) of the COMPASS study. This ongoing survey-based cohort study includes grade 9-12 students attending secondary schools in Alberta, British Columbia, Ontario, and Quebec in Canada. The survey questions cover multiple aspects of student health behaviours, including eating, sedentary behaviour, alcohol, tobacco, and marijuana use, bullying, academic performance, physical activity, BMI, and school connectedness. Study 1 applied k-means clustering analysis to establish student behaviour profiles, followed by a Random Forest model (RF) to identify the factors associated with the characteristics before and after COVID-19. Among the various student-level behaviour factors, Study 2 focused on self-reported BMI by predicting youth BMI status and identified associated factors using six supervised machine learning classifiers, K-Nearest Neighbour, Logistic Regression, Support Vector Machine, Random Forest, Multinomial Naïve Bayes, and Extreme Gradient Boosting (XGBoost) between Complete Case Analysis (CCA) and multiple imputation (MI) approaches. Since weight perception was identified as the most significant factor associated with BMI prediction in Study 2, Study 3 used weight perception as the outcome variable. This study explored the transition pattern of student weight perception and the associated factors through the Markov Chain, Multinomial Logistic Regression, and time-series deep learning models, including Recurrent Neural Networks (RNN) and Long Short-Term Memory (LSTM). The Shapley Additive Explanations (SHAP) analysis was applied for all three studies to assess the model interpretability. Results Study 1 found that in both pre-COVID (2018-19) and post-COVID (2020-21) cohorts, clusters were distinguished as closely involved with substance use and lower psychological well-being, including personal relationships with their families or unwillingness to discuss their mental health with an adult at school. However, the number of students in these clusters was relatively low compared to the other clusters, comprising only 0.5% of the pre-COVID cohort and 0.2% of the post-COVID cohort. In sub-clusters from the pre-COVID cohort that excluded substance use factors, students who skipped more than 20 classes, did not complete homework, and were involved in bullying were more likely to be grouped together in one sub-cluster compared to students without these behaviours. Additionally, those intending to lose weight, perceiving themselves as overweight,and being less active had higher odds of being in one sub-cluster compared to those without weight change intentions and who perceived their weight as about the right. In the sub-clusters of the post-COVID cohort, students with adverse mental health well-being, higher anxiety scores, self-reported overweight or obese BMI, and those failing to meet the guidelines of at least 60 minutes of physical activity per day were more likely to be grouped together in one sub-cluster compared to the students with the opposite behaviours. Moreover, students with increased cannabis use, less physical activity, lower flourishing scores and higher anxiety scores were more likely to be in one group relative to students who reported no change in cannabis use. Study 2 discovered that, among both CCA and MI approaches, XGBoost achieved the best performance in predicting BMI compared to those using Support Vector Machine (SVM) and Random Forest (RF). In CCA, it achieved an overall accuracy and ROC-AUC value of 0.64 and 0.78. The model performance was similar in MI and yielded an overall accuracy of 0.64 and ROC-AUC value of 0.79. Based on the SHAP summary plot, the most important predictors were weight perception, gender, and weight change intention in all three BMI classes, and the result was consistent in both CCA and MI. According to the SHAP summary plot, the most significant predictors in all three BMI classes were further explained by weight perception, gender and weight change intention. Students who perceived themselves as slightly or very overweight and were trying to lose weight were classified into the overweight and obese class, while model prediction on health weight BMI involved perceiving the right weight and not trying to change their weight. Additionally, gender was emerged as the most significant variable in the unknown BMI class, with model predicting that females and gender minorities were more likely to be categorized in the unknown weight class compared to male students. Study 3 used the MI approaches on the linked dataset. It found that although there was a moderate probability of transitioning from underweight or overweight to about the right weight and a minor probability of changing from underweight to overweight, most youths were more likely to stay in the same weight perception as the previous year. In addition, Study 3 identified predictors associated with weight perception transition over time. Students with underweight BMI, the intention of gaining weight and disagreement with discussing their problems with families in Year 1 had a higher likelihood of perceiving themselves as underweight in Year 2. While overweight and obese or unknown BMI students who had the intention of losing weight and decreased time on social media after COVID-19 in Year 1 were more likely to have an overweight perception in Year 2. Compared to peers who stayed at perceiving about the right weight in Year 2, underweight BMI students had higher odds of remaining underweight perception. In contrast, overweight BMI students with losing weight intention were likely to continue with an overweight perception and transition from about the right weight to an overweight perception. Students who wanted to gain weight were more likely to remain underweight or change from underweight to about the right weight. Notably, students with more participation in muscle-strengthening exercises had a lower likelihood of remaining overweight perception. Both deep learning models have shown the top significant variables in Year 1 and Year 2 were weight change intention, BMI, skipped breakfast for losing weight, and days in muscle training exercises predicting third-year weight perceptions. The intention of losing weight, higher BMI status such as overweight and obese or unknown, and more days in skipping breakfast for losing weight predicted students towards an overweight perception. In contrast, among the right weight perception group, students tended to stay the same weight or not try to do any weight change, had healthy BMI, had a lower number of days skipping breakfast, and had more days in muscle training. These results were consistent with the weight perception transition-associated predictors from the Multinomial logistic regression. Conclusion As the first study that focused on Canadian youth behaviour profiles, prediction of BMI and weight perception incorporating multiple machine learning techniques, the result of the dissertation disseminates key messages to the stakeholders who want to understand student behaviour profiles and focus on the preventive intervention on youth obesity. This research emphasized the importance of the school’s environment on youth’s behaviour and the tri-directional relationships among BMI, weight change intention, and weight perception, suggesting future analysis to emphasize these variables when developing healthy behaviour-related strategies. Overall, it illustrated the necessity of establishing educational programs related to BMI and weight perception at school to raise awareness of self-esteem and body image acceptance.
Modifiable behavioural factors and their association with depression and anxiety in Canadian undergraduate post-secondary students
(University of Waterloo, 2024-04-30) Gibson, Sandra; Leatherdale, Scott
Background: The mental health of post-secondary students is important for academic success and overall wellness. If post-secondary students are struggling with mental health concerns, these concerns can affect various aspects of university life including transitioning to post-secondary education, socialization and making connections, physical health, academic success, and student retention. Certain lifestyle behaviours identified as modifiable behavioural factors, or behaviours that are within the students’ control, such as sleep, physical activity, and substance use, may be valuable commodities to explore to proactively and positively improve the mental health and academic achievements of post-secondary students. Objective: This thesis explored the associations between depression and anxiety, and six modifiable behavioural factors (sleep, physical activity, cigarette smoking, e-cigarette use, marijuana use, and alcohol consumption) among female and male Canadian undergraduate post-secondary students. Method: Data from the 2019 National College Health Assessment (NCHA) Canadian Reference Group was analyzed using logistic regression models. Models, stratified by sex at birth, explored the association between depression as a mental health indicator and six modifiable behavioural factors (sleep, physical activity, cigarette smoking, e-cigarette use, marijuana use, and alcohol consumption) while controlling for relevant covariates. The same approach, also stratified by sex at birth, explored the association between anxiety as a mental health indicator and the six modifiable behavioural factors and covariates. Results: In this sample of Canadian undergraduate students, 53% of students reported depression and 71% of students reported anxiety. The main predictors of depression for female and male students were insufficient sleep, cigarette use, and marijuana use, but insufficient physical activity predicted depression only for female students. The main predictors of anxiety for female and male students were insufficient sleep, insufficient physical activity, cigarette use, and marijuana use. Alcohol consumption including binge drinking was either not significant or was found to have an inverse association with depression and anxiety for both sexes. Conclusion: Mental health is a serious problem among Canadian undergraduate post-secondary students. Both depression and anxiety are linked to several modifiable behaviours: sleep, physical activity, cigarette use, and marijuana use. These finding warrant the need for effective health campaigns, programming, and institutional policies that support student well-being and decrease mental health prevalence at post-secondary institutions.
Multi-level analysis of school characteristics, based on the Comprehensive School Health Framework, associated with physical activity in a large sample of Ontario and Alberta secondary school students
(University of Waterloo, 2021-12-20) Pirrie, Melissa; Leatherdale, Scott
Physical activity (PA) has many physical and mental health benefits, but only 24.4% of youth achieve the recommended minutes of moderate-to-vigorous PA (MVPA). Schools are an important context for changing modifiable health behaviours in youth and the Comprehensive School Health (CSH) framework outlines four inter-related components that schools can strengthen to facilitate better student health: social and physical environment; teaching and learning; partnerships and services; and healthy school policy. There has been no research identified that simultaneously evaluates all four components of CSH and their association with youth PA in a Canadian context. The objectives of this thesis were: (1) describe the prevalence of school-level factors within the CSH framework and their association with student PA (weekly MVPA and meeting the three PA recommendations) in a large sample of Ontario and Alberta secondary schools; (2) examine how youth MVPA changes over a three-year period, stratified by gender; (3) evaluate the school characteristics associated with preventing the decline in MVPA over time, guided by the CSH framework; (4) determine the proportion of students achieving all three PA recommendations at baseline who were still achieving them two years later; (5) determine the proportion of students not achieving all three PA recommendations at baseline who were achieving them two years later; and, (6) evaluate the school characteristics associated with achieving all three recommendations two years later for these two groups of students, stratified by gender. These objectives were met using student and school data from the COMPASS research platform, a large prospective cohort, and reported through a series of three manuscripts. The first manuscript was a cross-sectional study of 37,397 students in Grades 9 to 12 from 80 schools in the 2015/2016 cycle of COMPASS. Using descriptive and multilevel regression analyses (2-level: students within schools), it examined the prevalence of school characteristics guided by the CSH framework and the association between these characteristics and student PA. While some school characteristics were found to be nearly universal (e.g., presence of gymnasiums), many varied between schools, allowing for further analysis. School characteristics within all four pillars of CSH were significantly associated with PA for at least one student subgroup (gender/grade). The second manuscript was a longitudinal study of 17,661 students from 78 schools in the 2013/2014, 2014/2015, and 2015/2016 cycles of COMPASS who were in Grade 9 or 10 in 2013/2014 and participated for at least two of the three years. Using multilevel regression analyses (3-level: repeated measures within students within schools), this manuscript examined the association between school characteristics within the CSH framework and slope of weekly MVPA minutes over time. Student MVPA declined significantly across the three years for both male and female students. The school’s social environment, partnerships, and policies were associated with student MVPA over time, however the specific school factors and directions of associations varied by gender. The third manuscript was a longitudinal study of 9,870 students in Grades 9 and 10, from 78 schools, who participated in both the 2013/2014 and 2015/2016 cycles of COMPASS. Using multilevel regression analyses (2-level: students within schools), this manuscript examined the association between school characteristics and achieving all three national PA recommendations after two years (≥60 min of MVPA daily, vigorous PA ≥3 days/week, strengthening activities ≥3 days/week). The analyses were stratified by student gender and baseline PA status. While some school-level variables were associated with higher odds of achieving the PA recommendations (e.g., access to equipment, public health partnerships, staff time for health), other school-level variables were associated with lower odds of achieving the PA recommendations (e.g., providing showers). The findings of this dissertation support that modifiable school characteristics within the CSH framework are associated with student PA and can have an impact on the trajectory of student PA over time. With limited school resources and a need to improve student PA, these findings can inform schools of which improvements could have the greatest impact. Since there was no researcher-led intervention and only naturally occurring variability between schools was examined, there is a greater chance that these changes could be replicated and sustained by schools, which could be supported by communities of practice. Finally, many opportunities for future research have been presented within the dissertation.
Predicting Overweight and Obesity Among Youth in Ontario, Canada: Evidence from Cross-sectional and Longitudinal Analyses
(University of Waterloo, 2017-09-13) Laxer, Rachel; Leatherdale, Scott
The percentage of Canadian children and adolescents that are overweight or obese has increased dramatically since the 1980s, with approximately 25% of youth in Canada now characterised as overweight or obese. Canadian youth are engaging in multiple risk-taking behaviours, some of which are associated with an increased risk of overweight and obesity. The school environment has the potential to influence student body mass index (BMI) through implementation of comprehensive healthy school policies, programs, and practices in the domains of physical activity and healthy eating. Guided by a socio-ecological framework, this dissertation research aimed to examine: (1) how modifiable risk behaviours cluster into unique behavioural patterns in youth, and how these behavioural patterns are related to BMI; (2) the effect of engaging in unique clusters of risky behaviours on youths’ BMI trajectories; and, (3) the effect of modifying obesity-related school policies, programs, and practices on youths’ BMI trajectories. Three manuscripts addressed these objectives using linked student- and school-level data from the COMPASS Study (COMPASS). The first manuscript represents a cross-sectional analysis (2012/13), while the second and third manuscripts were longitudinal (2012/13 to 2014/15) in nature. The first manuscript assessed the prevalence and clustering of 15 modifiable risk behaviours using latent class analysis in a sample of 18,587 youth in grades 9 to 12. Four distinct classes emerged: Traditional School Athletes, Inactive Screenagers, Health Conscious, and Moderately Active Substance Users. Youth belonging to the Traditional School Athlete, Inactive Screenager, and Moderately Active Substance User clusters were all significantly more likely to be overweight or obese, compared to the Health Conscious group. The second manuscript examined the effect of engaging in the four clusters of risky behaviours at baseline on youths’ BMI trajectories, using a linked longitudinal sample of 5,084 students in Grades 9 and 10. Using linear mixed effects models, results identified a significant difference in BMIs only at baseline in the four clusters; despite these differences, BMI increased across all clusters annually by the same amount. The third manuscript examined the effect of modifying physical activity and nutrition-related programs, policies, and practices on BMI trajectories using a linked longitudinal sample of 4,951 students in Grades 9 and 10 attending 41 COMPASS schools. Between 2012/13 and 2013/14, 26 of 41 schools implemented distinct new programs or policies, none of which used a Comprehensive School Health Approach. Results indicate that none of these school modifications were associated with improved or reduced BMI trajectories. Findings of this dissertation research have implications for future public health and school-based interventions, and highlight the need for future research in this area, particularly focused on a Comprehensive School Health approach to obesity prevention. COMPASS is uniquely positioned to evaluate similar naturally occurring school-based interventions in a cost-effective and efficient, yet scientifically robust manner by following the same students as they progress through school and are exposed to a changing school environment.
Tanning Attitudes That Predict the Prevalence and Frequency of Tanning bed use in Older Adolescents and Young Adults in Canada
(University of Waterloo, 2016-06-09) Palubiski, Lisa; Leatherdale, Scott
Background: Tanning bed use is a modifiable risk factor in the development of melanoma skin cancer. Despite the increased risk of skin cancer, tanning bed use is most common among the adolescent and young adult population. Adolescents and young adults intentionally expose their skin to the artificial ultraviolet (UV) radiation emitted from tanning equipment. In Canada, the indoor tanning industry is largely unregulated and in need of a coordinated public health intervention. Objectives: The objective of the study was to estimate the prevalence and frequency of tanning bed use in the past 12 months and to identify the tanning attitudes that predict the prevalence and higher frequency of tanning bed use in the past 12 months in the older adolescent and young adult population in Canada. The purpose of the study was to identify key points of intervention and to provide valuable information to help inform policy makers and health promotion workers when developing a strategy to reduce exposure to artificial UV radiation. Methods: The study used the data collected in the 2006 Second National Sun Survey (NSS2), the most recent and comprehensive survey in Canada to examine exposure to UV radiation. A logistic regression and negative binomial regression model was used to predict the prevalence and higher frequency of tanning bed use in the past 12 months among older adolescents and young adults (aged 16 to 34) in the 2006 NSS2, respectively. Results: Overall, 21.5% of females and 8.3% of males (aged 16 to 34) in Canada were found to have had used artificial tanning equipment at least once in the past 12 months in 2006. Among those who had used a tanning bed in the past 12 months, 7.0% of iv females and 10.3% of males had used the equipment once, compared to 41.3% of females and 29.2% of males who had used the equipment more than 12 times. The individual level determinants that predict any use of a tanning bed in the past 12 months include gender (female), ethnicity (white), the intent to suntan during the summer months (always or often), the belief that people look better with a tan, and the belief that you look more attractive with a tan. In addition, having skin that will freckle (no suntan) when repeatedly exposed to sunlight was negatively associated with any use of a tanning bed in the past 12 months. The belief that a tan gives a healthy outdoor look, on the other hand, did not predict any tanning bed use in the past 12 months. Among those who had used a tanning bed in the past 12 months, the individual level determinants that predict the higher frequency of tanning bed use include gender (female), skin that will moderately tan when repeatedly exposed to sunlight, the use of a tanning bed to look better (reported as ‘very important’), and the use of a tanning bed to relax or feel better (reported as ‘very important’). The use of a tanning bed to boost their immune system, to protect against cancer, and to get vitamin D did not predict the higher frequency of tanning bed use in the past 12 months. Conclusion: Tanning bed use in the older adolescent and young adult population is a significant and growing public health concern both in Canada and worldwide. The appearance-related motivation to use a tanning bed, but not the health-related motivation to use a tanning bed, is predictive of tanning bed use and is a key point of intervention. The tobacco industry is similar to the indoor tanning industry; however, tobacco control efforts have led to the development of evidence-based policies, which may provide a framework to reduce tanning bed use.
Understanding youth tobacco and nicotine product use: Exploring susceptibility to, use of, and trajectories for six tobacco and nicotine products
(University of Waterloo, 2018-08-31) Cole, Adam Geoffrey; Leatherdale, Scott
One of the greatest accomplishments of public health has been the significant reductions in harms due to smoking. Although tobacco cigarettes have typically been the product with the highest prevalence of use, there remains a significant number of youth that use other products such as e-cigarettes, cigarillos or little cigars (CLCs), cigars, smokeless tobacco (SLT), and hookah. Past research has focused on tobacco cigarette smoking behaviours and has neglected investigating the use of other tobacco and nicotine products. The objectives of this dissertation were (1) to examine the ability of current susceptibility measures to predict the use of other tobacco and nicotine products, (2) to identify latent classes of tobacco and nicotine product use, and (3) to identify latent trajectory groups for the use of each product. Four manuscripts addressed these objectives for six tobacco products (i.e., tobacco cigarettes, e-cigarettes, CLCs, cigars, SLT, and hookah) using longitudinal data from students in Ontario that participated in the COMPASS study from 2013-2016. The first manuscript calculated the sensitivity, specificity, positive and negative predictive values of the susceptibility to smoking construct for the use of each tobacco and nicotine product. Results indicated that the sensitivity of the construct was moderate while the specificity was high. The positive predictive value was variable, depending on the prevalence of the product, while the negative predictive value was very high. Similar values were calculated for each measure of the susceptibility construct. The second manuscript identified student-level sociodemographic and behavioural characteristics of non-smoking youth at baseline that used each tobacco and nicotine product one- and two-years later. Given that the first manuscript provided evidence for the predictive validity of the susceptibility construct, this manuscript included susceptibility to future smoking as a predictor in the models. Baseline susceptibility to future smoking was strongly associated with the use of each tobacco product and e-cigarette at one- and two-year follow-up. Additionally, students that had friends that smoked cigarettes or who reported binge drinking at baseline had higher odds of reporting the use of each product at follow-up. The third manuscript identified tobacco and nicotine product use clusters for three consecutive years using latent class analysis. At baseline, a three-class model was identified as best [(1) non-current users; (2) current tobacco cigarette, CLC, and e-cigarette users; (3) current polyproduct users], while a four-class model was identified one-year [(1) non-current users; (2) current e-cigarette users; (3) current dual tobacco cigarette and CLC users; (4) current polyproduct users] and two-years later [(1) non-current users; (2) current dual tobacco cigarette and e-cigarette users; (3) current tobacco cigarette, CLC, cigar, and e-cigarette users; (4) current polyproduct users]. Results of the multinomial regression models indicate that students that reported having friends that smoked cigarettes, binge drinking, and using marijuana were more likely to be classified into a current use class relative to a non-current use class. The final manuscript identified latent trajectory groups for the use of each tobacco and nicotine product using latent trajectory analysis. Given the results of the first two manuscripts, measures of susceptibility to future smoking were included when identifying trajectory groups. Consistent across all products, five groups of users were identified: (1) non-susceptible non-users, (2) non-susceptible puffers, (3) stable low intenders, (4) escalating experimenters, and (5) consistent current users. Across all tobacco and nicotine products, students had the highest probability of remaining in the same group over time, although some transitions in group membership were evident. Results of the multinomial logistic regression models indicate that across all products, students that reported having friends that smoked cigarettes, binge drinking, and using marijuana were more likely to be classified into any other trajectory group relative to the non-susceptible non-users group. Additionally, students that reported a higher school connectedness score and eating breakfast every day in a usual school week were less likely to be classified into any other trajectory group relative to the non-susceptible non-users group. This dissertation fills an important gap with respect to our knowledge of other tobacco and nicotine product use among youth in Canada. The findings of this dissertation have implications for research and practice and highlight the need for inclusive tobacco control programming, particularly with respect to school-level prevention and cessation programs. Given than many youth reported using more than one tobacco or nicotine product and commonly reported binge drinking and using marijuana, multi-substance use programs are needed. In addition, given that students transition into and out of tobacco and nicotine product use throughout secondary school, consistent programming may be needed to discourage the initiation and escalation of tobacco and nicotine product use throughout adolescence.
Understanding Youth Trajectories of Alcohol Use: Evaluating the Impact of a Policy of Authorizing Alcohol Sales in Some Grocery Stores in Ontario
(University of Waterloo, 2019-08-29) Gohari, Mahmood Reza; Leatherdale, Scott
The latest change in the policy of the Liquor Control Board of Ontario (LCBO), enacted in December 2015, authorizes the sale of alcohol in 450 grocery stores that previously had not sold alcohol. This policy change increased the availability of alcohol to the province’s population in terms of the number of off-premise alcohol outlets, hours and days of sale. Since alcohol consumption is highly prevalent among Canadian youth, the new LCBO policy may result in a change in youth alcohol use patterns. The youth population is heterogeneous with respect to alcohol use patterns, and there exist several distinct patterns of alcohol use among youth each representing a subgroup of the population. As these subgroups differ in patterns of use, their responses to changes in alcohol-related policies could likewise differ. Given the numerous immediate and long-term adverse health outcomes associated with alcohol consumption, evaluation of the impact of the new LCBO policy on each subgroup of the population is a public health priority. The research presented in this dissertation research used longitudinal data to examine the impact of the new LCBO policy on youth alcohol use patterns in a quasi-experimental setting with two control groups, one in Ontario and the other in Alberta. The objectives were to (1) identify patterns of alcohol consumption among the youth population, (2) investigate differences in alcohol use patterns across secondary schools, (3) estimate the probabilities of transitioning between drinking patterns over time, (4) examine how individual- and school-level covariates predict patterns of alcohol use and transitioning between the patterns, and (5) evaluate any impact of the new LCBO policy on changes in the alcohol use patterns of youth in the exposed jurisdictions by means of pre- and post-policy assessment. Three manuscripts served these objectives all using student- and school-level data from the COMPASS study. The first manuscript identified latent classes (patterns) of youth alcohol consumption and investigated whether the size of latent classes vary by school. The multilevel latent class analysis identified four student-level latent classes and two school-level latent classes. Student-level classes of youth alcohol use were characterized as non-drinkers (had never consumed alcohol or did not drink in past year, 44.2% of the sample), light drinkers (initiated alcohol consumption at age 14 or later and consumed alcohol up to 3 times a month, with one time binge drinking, 41.8% of the sample), regular drinkers (initiated drinking before age 14 and consumed alcohol 1 to 3 times a week and undertook binge drinking 2 to 4 times a month,11.1% of the sample), and heavy drinkers (initiated drinking before age 14 and consumed alcohol on a nearly everyday basis, with binge drinking more than once a week, 2.9% of the sample). Two groups of schools were characterized, one as low-use [schools with a relatively large number of non-drinkers (n=40, 44.9% of schools)] and the other as high-use [schools with higher rates of regular and heavy drinkers (n=49, 55.1%)]. Male students (OR=1.30) and upper grades (OR=1.93) were significantly associated with membership in higher use groups. The number of off-premise alcohol outlets and the median household income was not significantly associated with membership in school-level latent classes. The second manuscript estimated the probabilities of maintenance or change between the identified drinking patterns two years before the LCBO policy change. Latent transition analysis of longitudinal data identified a similar number of latent classes with slightly different structures. LTA identified four latent classes: non-drinker, periodic drinker (reported drinking up to 3 times a month and no binge drinking), lower risk drinker (reported drinking up to 3 times a month and once or less than a month binge drinking), and high-risk regular drinker (reported drinking 1-3 times a week and binge drinking 2-4 times a month). The results of the second manuscript suggest that alcohol consumption tends to increase among those who start, but the volume of increase is not the same across all populations of youth. The greatest risk of increasing consumption was observed among the periodic drinker group: 40% of periodic drinkers demonstrated not only an increase in their consumption but also reported occasions of binge drinking at the follow-up year, when previously they had not engaged in binge drinking at all. Overall, the proportion of individuals engaged in some level of binge drinking rose from 21.2% at baseline to 33.9% at follow-up. The manuscript suggests that some youth do quit drinking or reduce the level of their consumption over time. Nearly 10% of low risk or high-risk regular drinkers were likely to have stopped drinking one year later at the follow-up. The results indicate that the use of either cigarettes or cannabis is markedly associated with greater risk of membership in higher risk drinking classes. The third manuscript examined changes in probabilities of transitioning between the four identified patterns of alcohol use among subpopulations in the exposed jurisdiction, using the two control cohorts (respectively in Ontario and Alberta) before and after the new LCBO policy. The transition probabilities estimated by latent transition analysis suggest that the new LCBO policy has no negative impact on the periodic and low-risk drinker groups that comprise 57% of the population. In contrast, there is a negative impact among non-drinker and high-risk regular drinker groups as the lowest and highest risk groups, respectively. In communities with alcohol available in grocery stores, the lowest risk group (non-drinker) were more likely to transition to the highest risk group (high-risk regular drinker), and individuals in the highest risk group indicated a higher likelihood of maintaining their behaviour. Comparison of the prevalence of high-risk regular drinking among the three cohorts indicated that youth in the exposed jurisdictions had the highest rate of increase during the follow-up years. This dissertation enhances our knowledge of alcohol use patterns in Canadian youth, the developmental stages of alcohol use over time, and the impact of the new LCBO policy on alcohol use patterns of the youth population. This work signals the need for continued efforts to delay alcohol initiation of abstainers as the primary prevention and to promote the transition from drinking to reducing or quitting among drinkers. This dissertation illustrates that following the increase in physical availability of alcohol in the jurisdictions exposed to the new LCBO policy, the probability of high-risk regular drinking among youth has increased. Abstainers in the exposed jurisdictions had a higher risk of being regularly engaged in high-risk drinking compared to youth in unexposed jurisdictions. Further, high-risk regular drinkers are more likely to maintain their behaviours following the policy change. This research provides scientific, documentary and timely evidence on the impact of the new alcohol policy on specific subgroups of the youth population separately. This evidence can fuel and support initiatives to reduce harm of youth alcohol consumption. Moreover, the analytic approach used offers a template for future evaluations of the impacts of public policy changes, for instance, to examine patterns of cannabis use in view of federal Cannabis legalization.