THE RELATION OF SMOKING, ALCOHOL-USE AND OBESITY TO RISK OF SIGMOID COLON AND RECTAL ADENOMAS

We conducted a case-control study, using 429 cases with histologically confirmed sigmoid adenoma, 75 cases with rectal adenoma, and 3101 con trols showing normal colonoscopy at least up to 60 cm from the anus. T he subjects were male Self-Defense Forces personnel aged 48-56 who rec eived a retirement health examination including a routine sigmoid- or colonoscopy. Lifestyle characteristics were ascertained by a self-admi nistered questionnaire. Smoking in the recent past (less than or equal to 10 years preceding the colonoscopy) and smoking in the remote past (> 10 years before the colonoscopy) were both significantly associate d with risk of sigmoid adenoma but not with rectal adenoma as a whole. After reciprocal adjustment for smoking in the two periods, only smok ing in the recent past was associated with both sigmoid colon and rect al adenomas. Odds ratios (OR) of sigmoid adenoma (and 95% confidence i nterval) for the categories of 0, 1-150, 151-250 and greater than or e qual to 251 cigarette-years were 1.0 (reference), 1.9 (1.3-2.8), 2.1 ( 1.4-3.0) and 3.0 (1.9-4.7), respectively (P for trend < 0.01), and tho se for rectal adenoma were 1.0 (reference), 1.2 (0.4-3.2), 3.5 (1.4-8. 5) and 2.0 (0.6-6.7), respectively (P for trend = 0.03). Alcohol use w as significantly positively associated with sigmoid adenoma, and insig nificantly associated with rectal adenoma. Body mass index was signifi cantly positively associated with sigmoid adenoma, especially large on es. No such association was found for rectal adenoma. These findings s uggest that smoking, especially in the recent past, and alcohol use ar e common risk factors for sigmoid colon and rectal adenomas while obes ity may be exclusively related to the growth of sigmoid adenoma.