Objectives: The purpose was to investigate the relation between glucose tolerance and risk of sigmoid colon adenomas, a well-established precancerous lesion, in Japanese men.
Methods: In the consecutive series of 7,637 men aged 48 to 59 years who received a preretirement health examination at four hospitals of the Self Defense Forces (SDF) in Japan from 1986 to 1994, we identified 821 cases of sigmoid colon adenomas and 4,372 controls with normal sigmoidoscopy or colonoscopy at 60 cm or more from the anus. Glucose tolerance status was classified as normal, impaired glucose tolerance (IGT), newly diagnosed non-insulin dependent diabetes mellitus (NIDDM), or diabetes mellitus under treatment, based on a 75g oral glucose tolerance test and medical history. Statistical adjustment was made for body mass index (wt/ht2), cigarette smoking, alcohol use, rank of the SDF, and hospital.
Results: Modest increases in adenoma risk were observed for newly diagnosed NIDDM and diabetes mellitus under treatment while there was no association between IGT and adenoma risk. When small (< 5 mm in diameter) and large (5+ mm) adenomas were analyzed separately, increased risk associated with newly diagnosed NIDDM was more pronounced for small adenomas, and diabetes mellitus under treatment showed a slightly stronger association with large adenomas.
Conclusions: The findings suggest that NIDDM is associated with modestly increased risk of sigmoid colon adenomas, and add to evidence that hyperinsulinemia increases colon cancer risk.