Association between physical activity and cancer risk among Chinese adults: a 10-year prospective study

In China, the quantity of physical activity differs from that in Western countries. Substantial uncertainty remains about the relevance of physical activity for cancer subtypes among Chinese adults. This study aimed to investigate the association between total daily physical activity and the incidence of common types of cancer. A total of 53,269 participants aged 30-79 years were derived from the Wuzhong subcohort of the China Kadoorie Biobank study during 2004-2008. We included 52,938 cancer-free participants in the final analysis. Incident cancers were identified through linkage with the health insurance system and death registries. Cox proportional hazard models were introduced to assess the associations of total daily physical activity with the incidence of 6 common types of cancer. During a follow-up of 10.1 years, 3,674 cases of cancer were identified, including 794 (21.6%) from stomach cancer, 722 (19.7%) from lung cancer, 458 (12.5%) from colorectal cancer, 338 (9.2%) from liver cancer, 250 (6.8%) from breast cancer, and 231 (6.3%) from oesophageal cancer. Compared to the participants in the lowest quartile of physical activity levels, those in the highest quartile had an 11% lower risk for total cancer incidence (hazard ratio [HR]: 0.89, 95% confidence interval [CI]: 0.81-0.99), 25% lower risk for lung cancer incidence (HR: 0.75, 95% CI: 0.60-0.94), and 26% lower risk for colorectal cancer incidence (HR: 0.74, 95% CI: 0.55-1.00). There were significant interactions of physical activity with sex and smoking on total cancer (both P for interaction