NEW YORK, Aug 16 (Reuters Health) -- Obesity is a risk factor for colon cancer in both men and women, reports a federal researcher.
Given the "high prevalence of obesity in the United States," these findings "bode ill for future trends in the incidence of (colon cancer)," according to researcher Dr. Earl S. Ford of the Centers for Disease Control and Prevention in Atlanta, Georgia. His data is published in the August 15th issue of the American Journal of Epidemiology.
Ford examined 1971-1992 data on over 13,000 Americans collected as part of the first National Health and Nutrition Examination Survey. Over the study period, 222 of the participants developed colon cancer.
Study subjects were divided into groups depending on their body mass index (BMI) -- a standard computation of body weight and fat expressed as weight in kilograms divided by height in meters squared. Persons with a BMI over 30 are typically considered obese. For example, a 5'6" woman weighing 190 pounds has a BMI of 30.
Ford reports that, compared with individuals with a BMI of 22, persons with a BMI of between 24 to 26 faced an 86% higher risk of developing colon cancer. Relative risks for persons with BMIs of between 26 to 28, or 28 to 30, were even higher -- more than double or triple those of individuals with a BMI of 22.
The findings add to existing evidence regarding a link between overweight and colon cancer risk, but extend this association to women. Most previous studies had linked obesity to colon cancer, but only in men.
"The role of obesity in the (development) of colon cancer is not well understood," Ford notes. Obesity may directly contribute to colon cancer risk by promoting cancerous changes in cells, he speculated, or it may simply be a 'marker' for other dangerous risk factors such as poor diet or lack of physical activity.
He believes that future studies should address whether or not weight loss can reduce the colon cancer risk of obese individuals. In the meantime, Ford told Reuters Health, "what I would suggest is that I think it would be reasonable for people who are overweight to pay particular heed to (colon cancer) screening recommendations."
Colorectal cancer screening recommendations from the American Cancer Society include: beginning at age 50, annual tests for blood in the stool, and sigmoidoscopy -- examination of the lining of the lower large intestine using a special, lighted instrument -- every 5 years. People with a family history of colon cancer may need to start screening at a younger age.
According to the American Cancer Society, nearly 100,000 new cases of colon cancer are diagnosed in the US each year, with deaths attributed to the disease topping 46,000 annually.
SOURCE: American Journal of Epidemiology 1999;150:390-398.
