Longitudinal associations between e-cigarette use, cigarette smoking, physical activity and recreational screen time in Canadian adolescents.

INTRODUCTION This study examined longitudinal associations between e-cigarette use, cigarette smoking, physical activity, and recreational screen time (ST) in a cohort of Canadian adolescents (ages 14-17 years; grades 9-12). METHODS Data from 5,951 adolescents who participated in COMPASS Year 4 (2015-16; baseline) and Year 6 (2017-18; follow-up) were used. Exposures included e-cigarette use and cigarette smoking. Outcomes included cut-points for moderate- to vigorous- physical activity (MVPA; ≥ 60 min/d), muscular strengthening exercises (MSE; ≥ 3 time/wk), participation in sport (SP; intramural or competitive), and recreational screen time (ST; ≤ 430 min/day). Generalized linear mixed models were performed. RESULTS E-cigarette use (16.6% vs 39.2%), cigarette smoking (0.9% vs 4.7%) and dual use (0.8% vs 4.1%) increased from baseline to follow-up. SP (70.8% vs 61.3%) and the prevalence of meeting MVPA (49.8% vs 42.1%) and MSE cut-points (54.0% vs 45.3%) decreased from baseline to follow-up. Recreational ST remained similar from baseline to follow-up. New e-cigarette use at follow-up was associated with maintenance of SP and meeting MVPA and MSE cut-points, but also with increased ST. New cigarette smoking at follow-up was associated with maintaining high ST and low SP. Cigarette smoking at baseline and follow-up was associated with maintaining high ST, low MSE, and low SP. Cigarette smoking cessation at follow-up was associated with increasing MVPA and MSE, decreasing ST, and maintaining low SP. CONCLUSION Given the clustering and co-occurring unhealthy behavioral patterns, intervention strategies to promote healthy lifestyles should take a holistic approach, by targeting multiple behavioral changes simultaneously. IMPLICATIONS This investigation highlighted that, unhealthy behaviors, particularly e-cigarette use, cigarette smoking, and excessive use of screens, tend to co-occur among Canadian adolescents. Therefore, intervention strategies to promote healthy lifestyles should take a holistic approach, by targeting multiple behavioral changes simultaneously particularly in school and community settings. As an exception, new and stable e-cigarette use appears to co-occur with achieving sufficient levels of physical activity. Increasing awareness about the risk of e-cigarette use may target population groups that are physically and socially active (e.g., athletes, sport teams).