Physical activity, obesity, and bladder cancer incidence

Cigarette smoking is an established risk factor for bladder cancer (BC), but evidence for physical inactivity and obesity is limited.

This analysis included 146,027 participants from the Cancer Prevention Study-II (CPS-II) Nutrition Cohort, a large prospective cohort of cancer incidence established in 1992. Multivariable-adjusted Cox proportional hazards models were used to examine associations between body mass index (BMI), moderate-to-vigorous intensity aerobic physical activity (MVPA), leisure-time spent sitting, and BC risk. Effect modification by stage, smoking status, and sex was examined.

Only participants accumulating 15.0- < 30.0 MET-hrs/wk of MVPA had a lower risk of BC overall (RR 0.88, 95% CI 0.78, 0.99, compared to > 0-7.5 MET-hrs/wk) in the fully adjusted models. When stratifying on BC stage, MVPA (15- < 30 MET-hrs/wk vs. > 0- < 7.5 MET-hrs/wk, RR 0.83, 95% CI 0.70-0.99) and excess sitting time (≥ 6 h/day vs. 0- < 3 h/day RR 1.22, 95% CI 1.02, 1.47) were associated with risk of invasive BC only. There was no consistent evidence for effect modification by smoking status or sex.

This study supports that MVPA and sitting time may play a role in BC incidence, but associations likely differ by stage at diagnosis. While additional studies are needed to confirm associations by stage, this study adds to the evidence of the importance of being physically active for cancer prevention.