Being overweight ups risk of colon cancer
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For men, the risk of colon cancer increases with body weight in a nearly linear manner, a study shows. For women, the risk is more variable but still trends upward, particularly for those younger than age 67.
The findings highlight the importance of weight control for colon cancer prevention, Dr. Kenneth F. Adams, of the National Institutes of Health in Rockville, Maryland, and colleagues conclude in a report in the American Journal of Epidemiology.
They examined the association between body mass index (BMI) and colorectal cancer incidence in 307,708 men and 209,436 women enrolled in the NIH-AARP Diet and Health Study. BMI, a standard measure to determine obesity, is calculated using weight and height. A BMI of more than 25 is considered overweight, and more than 30 is obese.
The men and women were followed from 1995 to 2000. During that time, a total of 2,314 men and 1,029 women developed colorectal cancer. An association was observed between BMI and an increased risk of colon cancer, but not rectal cancer, for both men and women.
For example, men who were overweight with a BMI of 25 to less than 27.5 had a 22 percent increased risk of developing colon cancer, compared to men of normal weight. Overweight men with a BMI of 27.5 to less than 30 had a 44 percent increased risk of colon cancer.
In obese men with BMIs of 30 to 32.5, 32.5 to less than 35, 35 to less than 40, and 40 or more, the risk of colon cancer was 53 percent, 57 percent, 71 percent, and more than 2-fold higher, respectively, relative to normal weight men.
For women, being overweight with a BMI of 25 to less than 27.5 was associated with a 29 percent increased risk of colon cancer. Overweight women with a BMI of 27.5 to less than 30 had a 31 percent increased risk of developing colon cancer.
In obese women with BMIs of 30 to 32.5, 32.5 to less than 35, 35 to less than 40, and 40 or more, the risk of colon cancer was 28 percent, 13 percent, 46 percent and 49 percent higher, respectively, relative to normal weight women.
“Age did not significantly modify the BMI-colon cancer association for men,” 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.”
SOURCE: American Journal of Epidemiology, July 2007.
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