DDW 2011: Higher BMI Associated with Colonic Adenoma Risk

Trial indicates that the relationship between body mass index and colonic adenomas is linear, suggesting that obesity can be a risk factor for colonic polyps.

The relationship between body mass index (BMI) and colonic adenomas appears to be linear, according to a retrospective study of 847 consecutive patients who presented for ambulatory colonscopies over a six-month period at Brooklyn Hospital Center, Brooklyn, New York, in 2009. The finding has implications for how often surveillance colonoscopies should be performed, according to Sreedevi Atluri, MD, a co-author with Mohammed K. Mazumder, MD, both of the Brooklyn Hospital Center, Brooklyn, NY.

Atluri noted during a poster presentation and interview at Digestive Disease Week 2011 that among the different polyp types, colorectal adenoma has proven to be a greater risk factor for development of adenocarcinoma of the colon as compared with hyperplastic polyps.

Atluri and colleagues collected data on BMI and the prevalence and type of polyps with the intent of identify significant correlations.

A normal BMI of ≤24.9 was found in 212 subjects. Polyps were found in 26%; adenomas in 9%, hyperplastic polyps in 12%, and both adenomas and hyperplastic polyps in 5%. Overweight BMIs of 25-29.9 were reported in 292 subjects. Among these, polyps were found in 35%, adenomas in 11%, hyperplastic polyps in 19%, and both in 6%. Among the 339 obese subjects with BMIs ≥30, polyps were found in 38%, adenomas in 15%, hyperplastic polyps in 17% and both in 6%.

Atluri noted that an inverse relationship was found between absence of polyps and BMI. Seventy-four percent of those with normal BMI had no polyps as compared with 61% among those with obese BMIs. In addition, there was a linear inverse relationship between colonic adenomas and BMI. The risk of developing an ademoma increased by >50% for those with obese BMIs as compared with normal BMIs. That relationship, however, was not found for hyperplastic polyps.

The linear inverse relationship between colonic adenomas and BMI does suggest that obesity can be a risk factor for colonic polyps, Atluri said. She commented further that with 66% of adults in the United States considered overweight or obese, these findings warrant a larger study to confirm them. If they are confirmed, guideline modifications may be justified, along with a stronger call for preventive measures to reduce obesity as a known risk factor for adenocarcinoma of the colon.

“Obesity, which is preventable through diet and other means, is definitely a risk factor for polyps. This,” she said, “poses a question to everyone: Should we change the interval for colonoscopies because we now know that obesity is a risk factor?” Colonoscopy interval recommendations in current guidelines, she noted, depend on the type and size of the polyp detetcted, but generally for an interval of every 5-6 years. But in these patients with high BMI, colonoscopy should be done earlier.” For someone who is obese with a history of polyps, the interval could perhaps be 3-5 years, Atluri suggested. While a few hyperplastic polyps do not confer added risk, detection of adenomas warrant yearly colonoscopies.

“Higher BMI and obesity should be further criteria for determining the interval for surveillance colonoscopies,” Atluri concluded.