A new study is the first to report a significant positive association between long sleep duration and the development of colorectal cancer, especially among individuals who are overweight or snore regularly. The results raise the possibility that obstructive sleep apnea may contribute to cancer risk.
“Our current study adds to the very limited literature regarding the relationship between sleep duration and/or sleep quality and colorectal cancer risk,” said lead author Xuehong Zhang, MD, ScD, instructor in the Department of Medicine at Harvard Medical School and associate epidemiologist at Brigham and Women’s Hospital in Boston. “The novel observation of increased risk among regular snorers who sleep long raises the possibility that sleep apnea and its attendant intermittent hypoxemia may contribute to cancer risk.”
The study, which appears in the May issue of the journal Sleep, utilized data from two prospective cohort studies, the Health Professionals Follow-up Study (HPFS) and the Nurses’ Health Study (NHS). A biennial questionnaire is sent to participants in each cohort to collect information on demographics, lifestyle factors and disease endpoints. Participants estimated their total hours of sleep in a 24-hour period and were asked if they snore.
A total of 76,368 women and 30,121 men formed the baseline population for this analysis. At baseline the median age was 53 years for women and 56 years for men. The researchers documented a total of 1,973 incident colorectal cancer cases: 1,264 cases in NHS (1986-2008) and 709 cases in HPFS (1988-2008). In subgroup analyses, men or women who were overweight or who were regular snorers and who reported sleeping 9 hours or more per day had approximately a 1.4 to 2-fold increased risk of developing colorectal cancer compared to overweight or regular snorers with 7 hours of sleep per day.
The American Academy of Sleep Medicine reports that individual sleep needs vary. However, the general recommendation is that most adults should get about seven to eight hours of nightly sleep.
The authors suggest that the association between the self-reported long sleep duration and incident colorectal cancer may be explained by obstructive sleep apnea, which involves repetitive episodes of complete or partial upper airway obstruction occurring during sleep despite an ongoing effort to breathe. The major predisposing factor for obstructive sleep apnea (OSA) is excess body weight, and loud snoring is a common symptom of sleep apnea.
Factors that may increase your risk of colon cancer include:
Older age. About 90 percent of people diagnosed with colon cancer are older than 50. Colon cancer can occur in younger people, but it occurs much less frequently.
African-American race. African-Americans have a greater risk of colon cancer than do people of other races.
A personal history of colorectal cancer or polyps. If you’ve already had colon cancer or adenomatous polyps, you have a greater risk of colon cancer in the future.
Inflammatory intestinal conditions. Chronic inflammatory diseases of the colon, such as ulcerative colitis and Crohn’s disease, can increase your risk of colon cancer.
Inherited syndromes that increase colon cancer risk. Genetic syndromes passed through generations of your family can increase your risk of colon cancer. These syndromes include familial adenomatous polyposis and hereditary nonpolyposis colorectal cancer, which is also known as Lynch syndrome.
Family history of colon cancer and colon polyps. You’re more likely to develop colon cancer if you have a parent, sibling or child with the disease. If more than one family member has colon cancer or rectal cancer, your risk is even greater. In some cases, this connection may not be hereditary or genetic. Instead, cancers within the same family may result from shared exposure to an environmental carcinogen or from diet or lifestyle factors.
Low-fiber, high-fat diet. Colon cancer and rectal cancer may be associated with a diet low in fiber and high in fat and calories. Research in this area has had mixed results. Some studies have found an increased risk of colon cancer in people who eat diets high in red meat.
A sedentary lifestyle. If you’re inactive, you’re more likely to develop colon cancer. Getting regular physical activity may reduce your risk of colon cancer.
Diabetes. People with diabetes and insulin resistance may have an increased risk of colon cancer.
Obesity. People who are obese have an increased risk of colon cancer and an increased risk of dying of colon cancer when compared with people considered normal weight.
Smoking. People who smoke cigarettes may have an increased risk of colon cancer.
Alcohol. Heavy use of alcohol may increase your risk of colon cancer.
Radiation therapy for cancer. Radiation therapy directed at the abdomen to treat previous cancers may increase the risk of colon cancer.
According to the authors, sleep disruption caused by OSA may reduce sleep quality and increase sleepiness, resulting in longer reported sleep durations. Furthermore, intermittent hypoxemia similar to that which occurs in OSA has been shown in animal models to promote tumor growth.
“Future studies should focus on different populations and evaluate to see whether sleep duration and sleep quality is a novel risk factor for colorectal cancer and to understand the mechanisms behind this association,” said Zhang.
Diet and Lifestyle: Studies suggest that diets high in red meat and fat (especially animal fat) and low in calcium, folate, and fiber may increase the risk of colon cancer. Also, some studies suggest that people who eat a diet very low in fruits and vegetables may have a higher risk of colon cancer. However, results from diet studies do not always agree, and more research is needed to better understand how diet affects the risk of colon cancer.
Inactivity and obesity have also been linked to higher risk of colon cancer. Studies have shown that daily physical activity can decrease colon cancer risk by as much as 50 percent.
Cigarette smoking: A person who smokes cigarettes may be at increased risk of developing polyps and colon cancer.
Because people who have colon cancer may develop colon cancer a second time, it is important to have checkups. If you have colon cancer, you also may be concerned that your family members may develop the disease. People who think they may be at risk should talk to their doctor.