There may be a link between high blood sugar levels and an increased risk of colorectal cancer in older women, a new study finds.

Researchers analyzed 12 years of data collected from 5,000 postmenopausal women in the U.S. Women’s Health Initiative study. The women’s fasting blood sugar (glucose) and insulin levels were measured at the start of the study and then several more times over the next dozen years.

During the study period, 81 of the women were diagnosed with colorectal cancer.

The researchers found that women with elevated glucose levels at the start of the study were more likely to develop colorectal cancer, and that those in the highest third of glucose levels were nearly twice as likely to develop colorectal cancer than those in the lowest third.

There was no association between insulin levels and colorectal cancer risk, according to the team led by researchers at Albert Einstein College of Medicine in New York City.

The study appears online Nov. 29 in the British Journal of Cancer.

Obesity - which is usually accompanied by elevated blood levels of glucose and insulin - is a known risk factor for colorectal cancer. It’s long been believed that the increased risk of colorectal cancer associated with obesity is due to high insulin levels, but this study suggests it may be due to high glucose levels.

“The next challenge is to find the mechanism by which chronically elevated blood glucose levels may lead to colorectal cancer,” lead author Geoffrey Kabat, a senior epidemiologist at Einstein, said in a medical college news release. “It’s possible that elevated glucose levels are linked to increased blood levels of growth factors and inflammatory factors that spur the growth of intestinal polyps, some of which later develop into cancer.”

Colorectal cancer is the third most commonly diagnosed cancer and the third leading cause of cancer death in the United States, according to the American Cancer Society.

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- Robert Preidt