Physical activity and subsequent risk of kidney, bladder and upper urinary tract cancer in the Japanese population: the Japan Public Health Centre-based Prospective Study.

Background: Although physical activity has been reported as a protective factor for kidney and bladder cancer in epidemiological studies, it is not clear.
Methods: In a population-based prospective study of 76,795 Japanese aged 45-74 years, participants were evaluated physical activity by self-administered questionnaire. Hazard ratios (HRs) and 95% confidence intervals (CIs) of the risk of urological cancer were calculated by the Cox proportional hazards models.
Results: During the 15.1-year follow-up, 202 kidney, 373 bladder and 83 upper urinary tract cancer cases were identified. Physical activity was not significantly associated with kidney, bladder and upper urinary tract cancer risks, with multivariate HRs in the highest versus lowest group of 1.05 (95% CI: 0.74-1.49), 1.06 (95% CI: 0.81-1.39) and 0.80 (95% CI: 0.48-1.35), respectively.
Conclusions: Physical activity was not associated with the risk of urological cancer in the Japanese population.