Long Sleep Duration Linked to Colorectal Cancer

Researchers have found a significant link between long sleep duration and colorectal cancer, particularly among people who snore or who are overweight. 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 and colleagues analyzed data from more than 100,000 men and women taking part in two prospective cohort studies. Results showed that people 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 who slept for 7-hours each day. The authors believe that the association between long sleep duration and incident colorectal cancer may be explained by obstructive sleep apnea (OSA), as intermittent hypoxemia, similar to that which occurs in OSA, has been shown to promote tumor growth in animal models. "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," concluded Zhang.