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Unusual Risk Factors for Colorectal Cancer

Risk factors for colorectal cancer

It’s not hard to understand how a poor diet can be a risk factor for colorectal cancer. But researchers have uncovered some new and unusual risk factors for colorectal cancer, and they leave you wondering why they pose a risk.

What are the new risk factors for colorectal cancer?

More than 140,000 people will be diagnosed with colon cancer or rectal cancer during 2013, according to the National Cancer Institute, and more than 50,000 will die of the disease. A list of risk factors (described later in this article) has been established to help individuals identify their chances of developing the disease and prompt them to be screened.

That said, scientists have identified a few new potential risk factors for colorectal cancer to add to the existing list, and they seem a bit unusual. The new additions come from researchers at Harvard Medical School and are described in a new edition of Sleep.

It appears that people who sleep at least 9 hours a night and who either snore or who are overweight are at increased risk of the disease. This finding was the result of an analysis of data from two long-running studies (22-year follow-up) that involved more than 106,000 health professionals.

A total of 1,973 cases of colorectal cancer developed over the study period. Although sleeping 9 or more hours per night, compared with 7 hours, was associated with a higher risk of colorectal cancer, that risk increased when snoring or a body mass index greater than 25 was added in. For example:

  • Men who slept 9 or more hours and who snored had a nearly twofold increased risk of colorectal cancer
  • Women who slept 9 or more hours and who snored had nearly a 2.5-fold increased risk
  • Long-sleeping men who were overweight had a 1.5-fold increased risk while long-sleeping overweight women had a slightly less increased chance of developing colorectal cancer

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Why did researchers see this greater risk of colorectal cancer in people with these specific factors? According to a statement by Xuehong Zhang, MD, ScD, of Harvard Medical School, this “novel observation” suggests “the possibility that sleep apnea and its attendant intermittent hypoxemia [insufficient level of oxygen in the blood] may contribute to cancer risk.”

Other risk factors for colorectal cancer
It may be too early to add long-sleeping plus snoring and being overweight to the list of colorectal cancer risk factors. For now, here are the factors generally recognized by the medical community.

  • Age: Although colorectal cancer can develop in young people, it is most common in individuals older than 50.
  • Gender: Men are more likely to develop rectal cancer and women have a higher risk for colon cancer.
  • Presence of polyps: The presence of noncancerous growths called polyps on the inner walls of the colon or rectum are common in people older than 50. One type of polyp, known as an adenoma, is considered a precursor toward colorectal cancer.
  • Diet: A high-fat, low-fiber diet has been associated with an increased risk.
  • Lifestyle habits: Smoking and alcohol use, being sedentary, and carrying excess weight are all risk factors for colorectal cancer.
  • Cancer history: Women with a history of breast, ovarian, or uterine cancer have a greater risk of developing colorectal cancer.
  • Diabetes: Having diabetes increases your risk of developing colorectal cancer by 30 to 40 percent.
  • Family history: If two or more of your family members have had colorectal cancer, your chances of developing the disease rise by about 20 percent.
  • Race: Individuals who are African-American have the highest incidence of colorectal cancer, while the lowest risk of the disease is among Asian-Americans, Hispanics, and Native Americans.

Also Read:
Spread of Colon Cancer Stopped by Tapeworm Drug
Osteoporosis Drugs May Reduce Colorectal Cancer Risk

This new study introduces the possibility that sleeping more than 9 hours a night, along with snoring or being overweight, may increase the risk of colorectal cancer. Everyone should be aware of all the risk factors for developing this often fatal disease.


Zhang X et al. Associations of self-reported sleep duration and snoring with colorectal cancer risk in men and women. Sleep 2013 May 1; 36(5): 681-88