Physical activity and occupational risk of colon cancer in Shanghai, China

Using occupational data for over 2000 colon cancer cases diagnosed between 1980 and 1984 in Shanghai, and employment information from the 1982 census for the Shanghai population, standardized incidence ratios (SIR) were computed for occupational groups classified by job types and physical activity levels. Men employed in occupations with low physical activity levels had modest but significantly elevated risks of colon cancer. SIR for jobs with low activity based on sitting time was 121 (95% confidence interval, Cl: 108-135) and based on energy expenditure was 126 (95% Cl: 115-138). Corresponding SIR for women were 99 (95% Cl: 83-118) and 113 (95% Cl: 100-127). The data were also used to screen for specific occupations with elevated SIR to generate leads to occupational colon cancer. Increased incidence was observed for professional and other white collar workers, and male chemical processors and female textile workers. The findings add to the emerging evidence that workplace activity may influence the risk of this common cancer.