A high body mass index is a more significant risk factor for colorectal cancer in women than in men, according to a presentation at the annual meeting of the American College of Gastroenterology.

The American researchers performed colonoscopies on a population of 2,300 asymptomatic adults (1,250 men, 1,050 women) and found increasing body mass index is associated with higher risk for significant colorectal neoplastic disease for women but the effect was not statistically significant for men.

The researchers divided the women into several groups based on index and evaluated whether screening tests detected large or multiple polyps, high-grade dysplasia, or cancer. Women who had a body mass index of 40 (threshold for obesity) or higher were 5.2 times more likely to have significant neoplasia detected during colonoscopy than women with an index of 25 or less (considered healthy weight) after adjustment for smoking, age, alcohol use, and family history.

Explaining the disparity in findings between men and women, Joseph C. Anderson, MD, one of the investigators, said, “We use body mass index as a surrogate measure for body fat. It may be that for men and women with similar body mass index, women have less muscle than men. This needs to be explored further.”

According to Anderson, the implications of this study are important for physicians counseling overweight and obese women about colorectal cancer screening in light of their increased risk.