Diabetes mellitus and risk of colorectal cancer in the Singapore Chinese health study.

The incidence of colorectal cancer is highest in populations that consume an energy-dense diet, have low intakes of vegetables and fruit, or lead a sedentary lifestyle. These factors may influence colorectal carcinogenesis via insulin pathways. We examined whether diabetes mellitus was associated with colorectal cancer in Singapore Chinese, whose body type and lifestyle profiles are distinct from those of Western populations. Between April 1993 and December 1998, 63,257 Singapore Chinese men and women aged 45 to 74 years were enrolled in a prospective study of diet and cancer. Each subject provided dietary, medical, and lifestyle information through an in-person interview. As of December 31, 2002, 636 incident colorectal cancer cases had been diagnosed. A history of physician-diagnosed diabetes was statistically significantly associated with colorectal cancer risk in both men (relative risk [RR] = 1.5, 95% confidence interval [CI] = 1.2 to 2.1) and women (RR = 1.4, 95% CI = 1.0 to 1.9). In stratified analyses, this association remained statistically significant among the subset of diabetics with high total calorie intake and low physical activity levels. Our results support the hypothesis that hyperinsulinemia may play a role in colorectal carcinogenesis, even in a relatively lean population.