NEW YORK (Reuters Health) Jul 05 - The risk of colon cancer increases with body mass index (BMI) in a nearly linear manner for men, according to results of a study published in the July issue of the American Journal of Epidemiology. For women, the risk is more variable but still trends upward, particularly for those less than 67 years old.
Dr. Kenneth F. Adams, of the National Institutes of Health in Rockville, Maryland, and colleagues examined the association between BMI and colorectal cancer incidence in a large, prospective cohort of 307,708 men and 209,436 women enrolled in the NIH-AARP Diet and Health Study.
The cohort was followed from 1995 to 2000. During that time, a total of 2314 cases of colorectal cancer occurred in men and 1029 cases in women. An association was observed between BMI and an increased risk of incident colon cancer, but not rectal cancer, for both men and women.
Specifically, the relative risks of colon cancer for a BMI of 18.5 to <23, 23 to <25, 25 to <27.5, 27.5 to <30, 30 to <32.5, 32.5 to <35, 35 to <40, and 40 or more were 1.0 (referent), 1.11, 1.22, 1.44, 1.53, 1.57, 1.71, and 2.39, respectively, for men (p < 0.0005).
For women, the corresponding relative risks were 1.0, 1.20, 1.29, 1.31, 1.28, 1.13, 1.46, and 1.49 (p = 0.02).
"Age did not significantly modify the BMI-colon cancer association for men," Dr. Adams and colleagues report. "By contrast, colon cancer was associated with BMI in women aged 50 to 62 and 63 to 66 years, but not in those aged 67 to 71 years," they note.
The association was not modified by hormone replacement therapy in women, or by physical activity in men or women -- "indicating the importance of weight control as a prevention strategy for this very common malignancy."
Am J Epidemiol 2007;166:36-45
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