People who slept less than six hours a night were more likely to have dangerous polyps in their colon or rectum compared to better-rested patients, in one recent study.

The polyps, called colorectal adenomas, progress to become cancerous tumors in about 10% of cases. As a result, they are considered to be “precancerous” polyps and a strong predictor of the disease.

The findings don’t prove that lack of sleep causes these polyps to occur. The scientists note in the journal Cancer that this is the first time anyone has ever found a link between sleep duration and risk of colorectal adenomas, and the findings need to be confirmed in other studies.

Still, they say, the results indicate that people who don’t sleep much at night might have the same chance for developing colorectal cancer as other high-risk groups, such as people with a close relative who has been diagnosed with the disease or those with a diet high in red meat.

“Even if this is causal, it doesn’t necessarily mean you’ll get colon cancer,” said Dr. Li Li, associate director of the Case Comprehensive Cancer Center at Case Western Reserve University, in Cleveland, who headed the research team. “But if you get enough sleep it could prevent polyps, which could prevent colon cancer.”

How sleep and polyps might be connected isn’t clear, Dr. Li said. One of his hypotheses didn’t pan out in the study: a theory that poor sleep would be linked to obesity and insulin resistance (when insulin manufactured by the body becomes less effective at controlling blood sugar levels, because the cells no longer respond to it properly). Both of these problems are known to increase the risk of colorectal cancer.

Some evidence has shown that the sleep hormone melatonin may protect against colorectal tumors, a lead Dr. Li said he hopes to explore further.

More than 140,000 Americans will be diagnosed with colorectal cancer this year, and some 51,000 will die from the disease, according to the National Cancer Institute.

In the latest research, Dr. Li and his colleagues studied 1240 men and women who came to their hospital for routine colonoscopy, an examination in which a camera is used to inspect the large intestine.

Prior to the exam, volunteers in the study underwent a variety of tests, including blood work and a detailed behavior survey that included questions about the duration, quality and other aspects of sleep.

Overall, the researchers found adenomas in 338 people, or 27 percent of the entire group. Analyzing the sleeping patterns of the subjects, they found a higher rate of these polyps in people who reported getting less than six hours of sleep (29 percent) than in those who said they slept seven or more hours nightly (22 percent).

The difference in sleep time between polyp patients and those without the lesions was small, only 19 minutes, on average, Dr. Li said. But more polyp patients reported sleeping much less than six hours, while few said they slept more than seven.

Dr. J. Leonard Lichtenfeld, deputy chief medical officer at the American Cancer Society, called the study “intriguing” and worthy of additional research. However, he stressed, the findings are by no means conclusive and the average differences in sleep times observed were small. That suggests that what looks like an effect of sleep might in fact reflect some other factor the researchers were unable to measure.

“Although the authors mention that sleep may need to be considered as a risk factor,” he said, “I think there’s a lot more work that has to be done before we can endorse that position.”

Cancer is a publication of the American Cancer Society, but Dr. Lichtenfeld said he had no editorial influence over the journal. Dr. Li’s research was funded by a grant from the National Cancer Institute.

SOURCE:  Cancer, online October 8, 2010.