Daily sedentary time and its association with risk for colorectal cancer in adults: A dose–response meta-analysis of prospective cohort studies

Sedentary behavior is emerging as an independent risk factor for health. However, previous studies have indicated that sedentary behaviors are associated with the colorectal cancer risk, but presented controversial results. Studies in PubMed and EMBASE were searched update to February 2017 to identify and quantify the potential dose–response association between daily sedentary time and colorectal cancer. Twenty-eight eligible studies involving a total of 47,84,339 participants with 46,071 incident cases were included in this meta-analysis. Our results showed statistically significant association between prolong television viewing time and colorectal cancer (odds ratio [OR] 1.17, 95% confidence interval [CI] 1.09–1.24, P < .001). Additionally, we obtained the best fit at an inflection point of 2 hours per day in piecewise regression analysis, the summary relative risk (RR) of colorectal cancer for an increase of 2 hours per day television viewing was 1.07 (95% CI 1.05–1.10, P < .001). Furthermore, prolong occupational sitting time was correlated with a significantly higher risk of colorectal cancer (OR 1.15, 95% CI 1.08–1.22, P < .001), increasing 2 hours per day of occupational sitting time per day was associated with a 4% incremental in the risk of colorectal cancer (RR 1.04, 95% CI 1.01–1.08). Additionally, prolong total sitting time was associated with a significantly higher risk of colorectal cancer (OR 1.06, 95% CI 1.03–1.09, P < .001). Increasing 2 hours of total sitting time per day was associated with a 2% incremental in the risk of colorectal cancer (RR 1.02, 95% CI 1.01–1.06). Subgroup meta-analyses in study design, study quality, number of participants, and number of cases showed consistent with the primary findings. Prolonged television viewing, occupational sitting time, and total sitting time are associated with increased risks of colorectal cancer.