An inadequate¹（不充分的） amount of sleep has been associated with higher risks of obesity², heart disease, diabetes³, and death. Now colon⁴ cancer can be added to the list. In a ground-breaking new study published in the Feb. 15, 2011 issue of the journal Cancer, researchers from University Hospitals (UH) Case Medical Center and Case Western Reserve University School of Medicine, found that individuals who averaged less than six hours of sleep at night had an almost 50 percent increase in the risk of colorectal（结肠直肠的） adenomas（腺瘤） compared with individuals sleeping at least seven hours per night. Adenomas are a precursor⁵ to cancer tumors, and left untreated, they can turn malignant⁶.

"To our knowledge, this is the first study to report a significant association of sleep duration and colorectal adenomas," said Li Li, MD, PhD, the study's principal investigator⁷, family medicine physician in the Department of Family Medicine at UH Case Medical Center and Associate Professor of Family Medicine, Epidemiology and Biostatistics at Case Western Reserve University School of Medicine. "A short amount of sleep can now be viewed as a new risk factor for the development of the development of colon cancer."

In the study, patients were surveyed by phone prior to coming into the hospital for scheduled colonoscopies at UH Case Medical Center. They were asked demographic（人口统计学的） information as well as questions from the Pittsburg Sleep Quality Index (PSQI), which obtains information about the patient's overall sleep quality during the past month. The PSQI asks for such information as how frequently one has trouble sleeping and how much sleep one has had per night. The study was funded by the National Cancer Institute through Case Western Reserve University School of Medicine.

Of the 1,240 patients, 338 were diagnosed with colorectal adenomas at their colonoscopy. The patients with adenomas were found in general to have reported sleeping less than six hours compared to compared to those patients without adenomas (control) patients, and the association between amount of sleep and adenomas remained even when adjusted for family history, smoking, and waist-to-hip ratio (a measurement of obesity).

The researchers also found a slightly stronger association of sleep duration with adenomas with women compared to men, but the difference was not statistically⁸ significant.

Dr Li said the magnitude of the increase in risk due to less hours of sleep is comparable to the risk associated with having a first-degree relative (parent or sibling) with colon cancer, as well as with high, red meat intake⁹. "Short sleep duration is a public health hazard leading not only to obesity, diabetes and coronary heart disease（冠心病） , but also, as we now have shown in this study, colon adenomas," he said. "Effective intervention¹⁰ to increase duration of sleep and improve quality of sleep could be an under-appreciated avenue for prevention of colorectal cancer."

Although why fewer hours of sleep may lead to colon cancer is unknown, Dr. Li said some of theories include that less sleep may mean less production of melatonin（褪黑激素） , a natural hormone¹¹ that in animals has been linked to DNA¹² repair, or that insulin resistance may underlie¹³ the link between sleep disturbance¹⁴ and cancer development.