Combined lifestyle factors and risk of incident colorectal cancer in a Chinese population.

A body of research links dietary intake, alcohol consumption, smoking, physical activity, body mass index (BMI), and possibly sleep patterns with colorectal cancer risk. However, little research has examined the association of the combination of these lifestyle factors with incidence of colorectal cancer, especially in non-Western populations. A protective lifestyle factor index of these six aforementioned factors was created and examined in relation to risk of developing colorectal cancer. This study is a prospective observational study of 50,466 Chinese men and women in Singapore ages 45 to 74 years during enrollment in the Singapore Chinese Health Study in 1993-1998 and followed up through 2007. The main outcome measures were standardized rates and HRs of incident colorectal cancer. The protective levels of each lifestyle factor were independently associated with reduced age- and sex-standardized incidence rates of colon cancer. When all the factors were combined into a single protective lifestyle factor index, there was a strong, monotonic decrease in incidence rate of colon cancer with an increasing score. Relative to participants with an index score of 0 to 3, the HRs (95% confidence intervals) of colon cancer for an index score of 4, 5, 6, 7, 8, and 9/10 were 0.58 (0.35-0.95), 0.56 (0.36-0.86), 0.50 (0.33-0.76), 0.43 (0.28-0.66), 0.39 (0.25-0.63), and 0.25 (0.12-0.54; P(trend) < 0.0001). The results were consistent by sex. Conversely, there was no association with rectal cancer risk. An increasing protective lifestyle factor index score is associated with a marked decreased risk of developing colon cancer in Chinese men and women.