The association of physical activity and body mass index with the risk of large bowel polyps.
OBJECTIVE
Several studies have suggested that physical inactivity and obesity increase the risk for colorectal neoplasia. In this study, we investigated the association of physical activity and body mass index (BMI) with the risk of different types of large bowel polyps. We did an observational analysis nested within a randomized double-blind placebo-controlled chemoprevention trial among patients with one or more recently resected histologically confirmed colorectal adenoma. Nine hundred thirty patients were randomized to calcium (1,200 mg/d, as carbonate) or placebo. Follow-up colonoscopies were conducted approximately 1 and 4 years after the qualifying examination. At study entry, we obtained each subject's current body weight and height, which we used to calculate BMI. After the second study colonoscopy, we asked subjects questions about their leisure time physical activity. Seven hundred eighty-seven subjects completed at least part of the physical activity questionnaire.


RESULTS
We found no association between measures of physical activity or BMI and tubular adenomas or hyperplastic polyps. However, among men, there were strong inverse associations observed between physical activity and advanced neoplastic polyps. Compared with men whose total daily energy expenditure was in the lowest tertile, those in the highest tertile had a risk ratio of 0.35 (95% confidence interval, 17-0.72); there was no similar reduction observed among women (risk ratio, 1.21; 95% confidence interval, 0.36-4.03; P for interaction = 0.04).
We found a significant inverse relationship between several measures of physical activity and risk of advanced colorectal neoplasms, particularly among men. No associations were found between BMI and hyperplastic polyps, tubular adenomas, or advanced neoplastic polyps.
Wallace
Kristin
K
Community and Family Medicine, Dartmouth Hitchcock Medical Center, Lebanon, NH 03756, USA.
Baron
John A
JA
Karagas
Margaret R
MR
Cole
Bernard F
BF
Byers
Tim
T
Beach
Michael A
MA
Pearson
Loretta H
LH
Burke
Carol A
CA
Silverman
William B
WB
Sandler
Robert S
RS
D000368:Aged; D015992:Body Mass Index; D002119:Calcium Carbonate / Q000627:therapeutic use; D018890:Chemoprevention; D003111:Colonic Polyps / Q000209:etiology* / Q000517:prevention & control*; D015444:Exercise; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009765:Obesity / Q000150:complications; D010809:Physical Fitness; D012307:Risk Factors; D012737:Sex Factors
D002119:Calcium Carbonate