Obesity and adenomatous polyps of the sigmoid colon.

The relation between obesity and adenomatous polyps of the sigmoid colon was investigated in male self-defense officials who received a retirement health examination at three hospitals of the Self-Defense Forces in Japan between January 1991 and December 1992. Body mass index (BMI) and waist-hip circumference ratio (WHR) were used as indices of obesity. A total of 228 adenoma cases and 1484 controls with normal sigmoidoscopy were identified in 2228 men: cases having small adenomas (< 5 mm in diameter) and those with large adenomas (5 mm or greater) numbered 115 and 102, respectively. Smoking, alcohol use, physical activity, rank, and hospital were controlled for by multiple logistic regression analysis. BMI and WHR were classified into four levels using the 30th, 60th, and 90th percentiles of each distribution in the control as cut-off points. There was a significant two-fold elevation in the overall adenoma risk among men at the highest BMI level (> or = 26.95) compared with those at the lowest level (< 22.48), but the risk did not linearly increase: a similar increase was also noted for large adenomas. While WHR was only weakly related to the overall adenoma risk, the risk of large adenomas progressively increased with increasing levels of WHR; odds ratio (OR) 2.9 (95% confidence interval (CI) 1.4-5.9) for the highest (> or = 0.958) versus lowest (< 0.878) levels. BMI was not materially associated with adenoma risk after additional adjustment for WHR, but a positive association between WHR and large adenomas was independent of BMI: OR 3.4 (95% CI 1.5-7.6) for the highest versus lowest levels. These findings suggest that obesity is associated with an increased risk of colon adenomas, probably with adenoma growth.