A total of 29% of those with diabetes had at least one adenoma, compared with 21% of those without diabetes.
People with diabetes also had more adenomas and more advanced adenomas than those who were diabetes-free.
The association between diabetes and precancerous colon growths remained after taking into account age, weight, and race -- three factors that affect diabetes risk.
Francis C. Okeke, MD, a research fellow at the Veterans Affairs Medical Center in Bronx, N.Y, presented the findings here at the annual meeting of the American College of Gastroenterology.
No Cause and Effect
Other studies have linked diabetes to precancerous colon growths and colon cancer, but the results have been inconsistent.
None proves that diabetes causes or directly contributes to adenoma growth or colon cancer.
"Diabetes and adenomas are two very common conditions. But we need more data before we can say one causes the other," says March Seabrook, MD, a gastroenterologist in Columbia, S.C. He was not involved with the research.
The analysis took into account some, but not all, diabetes risk factors that could affect the results, Seabrook tells WebMD.
The Role of Insulin
Okeke tells WebMD that insulin and other hormones might explain the link between diabetes and precancerous colon growths.
People with diabetes often have high levels of the blood-sugar-regulating hormone insulin, for example. High levels of insulin may promote the growth of cells, including precancerous and cancer cells, he says.
Still, "more study is needed," Okeke says.
For now, people with diabetes should continue to follow general recommendations for colon cancer screening, Seabrook says.
The guidelines call for screening to begin at age 50 if there are no risk factors, he says. Diabetes is not currently a risk factor.
If the findings are validated and diabetes does turn out to cause precancerous colon growths or colon cancer, "we may have to screen people with diabetes at a younger age, and at shorter intervals, than people without diabetes," Seabrook tells WebMD.
A total of 25.8 million Americans have diabetes, according to the American Diabetes Association. Over 1.1 million have colorectal cancer, according to the American Cancer Society.
The new study was presented at a medical conference. They should be considered preliminary as they have not yet undergone the "peer review" process, in which outside experts scrutinize the data prior to publication in a medical journal.
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