Associations of daily walking and television viewing time with liver cancer mortality: findings from the Japan Collaborative Cohort Study

Several studies have suggested that daily vigorous physical activity reduces the risk of liver cancer, whereas sedentary behavior increases the risk of several cancers. However, the link between liver cancer and low-intensity physical activity (walking) and sedentary behavior is unclear. Therefore, we explored the links between liver cancer mortality and daily walking time/television (TV) viewing time in Japanese adults aged 40-79 years in a large-scale nationwide cohort study. We excluded participants with a history of liver disease, cancer, stroke, or myocardial infarction at baseline (1988-1990) and those who died within the first 5 years of follow-up. A total of 69,752 adults (28,642 men and 41,110 women) were enrolled and followed for a median of 19.4 years. The Cox proportional hazards model was used to calculate hazard ratios (HRs) and 95 % confidence intervals (CI) for liver cancer mortality adjusted for age, sex, and other possible confounding factors. During the study period, 267 participants died of liver cancer. The HRs of participants who walked for > 0.5 h/day and watched TV for 2-4 versus < 2 h/day were 0.58 (95 % CI 0.39-0.89) and 0.58 (95 % CI 0.35-0.98), respectively, compared with those who walked for < 0.5 h/day and watched TV for > 4 h/day. Our findings suggest that longer walking times and shorter TV viewing times may reduce the risk of liver cancer.