Physical Activity and Cancer Incidence in Alberta's Tomorrow Project: Results from a Prospective Cohort of 26,538 Participants.

Background: Physical activity (PA) has been associated with lower risks of several cancers. We examined the association between total and domain-specific PA and risk of all and site-specific cancer risk.
Methods: We analyzed baseline data from Alberta's Tomorrow Project. Specifically, adults ages 35-69 years who completed the Past Year Total Physical Activity Questionnaire were included (n = 26,538). For each activity, participants reported the type, duration, and intensity of PA. Total, recreational, and occupational PA metabolic equivalent hours/week were divided into quartiles. Incident cancer cases up to December 2016 were identified via linkage to the Alberta Cancer Registry. The associations of PA on cancer risk were examined using Cox proportional hazards models.
Results: A total of 2,186 participants (8.24%) developed cancer during follow-up from 2001 to 2016. We observed a significant inverse association between total PA and all-cancer incidence in the multivariate-adjusted model [HRQ4vQ1 = 0.87; 95% confidence interval (CI): 0.76-0.99] that remained significant in the latency multivariate-adjusted model. Higher recreational PA was associated with a risk decrease for all-cancer in the latency multivariate-adjusted model (HR = 0.84; 95% CI: 0.74-0.96), and showed a linear inverse association with breast cancer. While none of the HR estimates for quartiles of occupational PA and all-cancer reached statistical significance, the model Ptrend was marginally significant in the latency multivariate-adjusted model (P = 0.06).Conclusions: In this cohort of Albertans, higher total PA and recreational PA appears to convey modest protection against the development of all-cancer.Impact: Public health and cancer prevention efforts should focus on encouraging population-level increases in PA. Cancer Epidemiol Biomarkers Prev; 27(8); 945-54. ©2018 AACR. ©2018 American Association for Cancer Research.