For people who are overweight or who snore, sleeping for too many hours a night could raise the risk of colorectal cancer, according to a new study.
Researchers from Harvard Medical School found that for these people, sleeping for nine or more hours per night is associated with a 1.4 to 2.4 times higher colorectal cancer risk, compared with similar people who sleep for an average of seven hours per night.
These findings suggest "the possibility that sleep apnea and its attendant intermittent hypoxemia may contribute to cancer risk," study researcher Xuehong Zhang, M.D., Sc.D., who is an instructor in the Department of Medicine at Harvard Medical School, said in a statement.
Zhang explained the relationship: People who have obstructive sleep apnea may tend to sleep longer because they are experiencing disturbed sleep throughout the night, and therefore are sleepier than people without the sleep disorder. And intermittent hypoxemia has been shown in animal studies to have connections with the growth of tumors.
The study, published in the journal SLEEP, is based on data from 76,368 women and 30,121 men; the average age of the women in the study was 53 and the average age of the men was 56. Among the total group, there were 1,973 new colorectal cancer cases.
There is no exact amount of hours of sleep adults should get each night, though it is generally recommended to get between seven and nine hours a night, according to the National Sleep Foundation. However, both sleeping too little and too much has been linked with other health woes, including heart risks, obesity, diabetes and even mortality, Greatist reports.