FRIDAY, Sept. 1 (HealthDay News) -- Type 2 diabetes is associated with increased risk of colorectal cancer, especially in men, and even more so among those who are current or former smokers, according to a study published in the August issue of the American Journal of Gastroenterology.
Paul J. Limburg, M.D., M.P.H., of the Mayo Clinic College of Medicine in Rochester, Minn., and colleagues conducted a study of 997 men and 978 women who lived in Rochester and were diagnosed with type 2 diabetes between 1970 and 1994. The subjects were followed up until the end of 1999 or until they died or emigrated.
Rates of colorectal cancer among the cohort were compared with those of the general population in Rochester. The study generated 19,158 person-years of follow-up, during which time 51 incident cases of colorectal cancer were identified within the type 2 diabetes cohort, to give a standardized incident ratio (SIR) of 1.39, although only 36.8 cases were expected.
Men in the type 2 diabetes cohort had a higher risk of overall and proximal colorectal cancer, with SIRs of 1.67 and 1.96, respectively. However, among women, type 2 diabetes did not significantly increase risk of colorectal cancer. Current and former smokers in the cohort were at higher risk for colorectal cancer; the SIR for smokers was 1.77, versus 0.99 for those who never smoked.
"Cigarette smoking appeared to positively modify diabetes mellitus-associated colorectal cancer risk, which to our knowledge has not been previously reported," the authors write.