Television Viewing Time and the Risk of Colorectal Cancer Mortality among Japanese Population: The JACC Study

PURPOSE: Sedentary behavior attributes to the increased risk of some cancers and all-cause mortality. The evidence is limited for the association between television (TV) viewing time, a major sedentary behavior, and risk of colorectal cancer death. We aimed to examine this association in Japanese population. MATERIALS AND METHODS: A prospective cohort study encompassed of 90,834 men and women aged 40–79 years with no prior history of colorectal cancer who completed a self-administered food frequency questionnaire, and provided their TV viewing information. The participants were followed-up from 1988–1990 to the end of 2009. The hazard ratios (HRs) and 95% confidence intervals (CIs) were calculated by the Cox proportional hazard regression for risk of colorectal cancer mortality according to TV viewing time. RESULTS: During the median 19.1-year follow-up period, we documented 749 (385 men and 364 women) colorectal cancer deaths. The multivariable-adjusted HRs for mortality from colorectal cancer were 1.11 (0.88–1.41) for 1.5 to < 3 hr/day, 1.14 (0.91–1.42) for 3 to < 4.5 hr/day and 1.33 (1.02–1.73) for ≥ 4.5 hr/day in comparison to < 1.5 hr/day TV watching; p-trend=0.038, and that for 1-hour increment in TV viewing time was 1.06 (1.01–1.11). Moreover, the multivariable-adjusted HR (95% CI) of colon cancer for 1-hour increment in TV viewing time was 1.07 (1.02–1.13). Age, body mass index, and level of leisure-physical activity did not show significant effect modifications on the observed associations. CONCLUSION: TV viewing time is associated with the increased risk of colorectal cancer mortality among Japanese population, more specifically colon rather than rectal cancer.