Diabetes and Colorectal Cancer Incidence in the Cohort of Swedish Men
- 1Division of Nutritional Epidemiology, The National Institute of Environmental Medicine, Karolinska Institutet, Stockholm, Sweden
- 2Departments of Nutrition and Epidemiology, Harvard School of Public Health, Boston, Massachusetts
- 3Department of Medicine, Channing Laboratory, Brigham and Women’s Hospital and Harvard Medical School, Boston, Massachusetts
- Address correspondence and reprint requests to Susanna C. Larsson, Division of Nutritional Epidemiology, The National Institute of Environmental Medicine, Karolinska Institutet, P.O. Box 210, SE-171 77 Stockholm, Sweden. E-mail:
Dietary and lifestyle factors related to insulin resistance and hyperinsulinemia, including a westernized diet, physical inactivity, and obesity, have been linked to increased colorectal cancer risk (1,2). These observations support the hypothesis that hyperinsulinemia (3) or factors associated with insulin resistance, such as hyperglycemia or hypertriglyceridemia (4), may play a role in colorectal carcinogenesis. Epidemiologic studies have observed an elevated risk of colorectal cancer associated with high circulating insulin and C-peptide (a marker of insulin secretion) concentrations (5–7). Also, a recent study (8) reported that chronic insulin therapy was related to a significant increased risk of colorectal cancer among patients with type 2 diabetes.
Some, but not all, epidemiologic studies have observed an increased risk of colorectal cancer among people with diabetes (9). However, several previous investigations were limited by small sample size and an inability to account for important covariates (9). In addition, few studies have reported on diabetes in relation to subsites in the colon, and the findings have been conflicting (10–13). We therefore examined the relationship between self-reported diabetes and risk of colorectal cancer overall and by subsite in the COSM (Cohort of Swedish Men).
RESEARCH DESIGN AND METHODS
The COSM was initiated in the autumn of 1997 when all men aged 45–79 years residing in Västmanland and Örebro counties in …