MEN who sleep for more than 10 hours per night on average, who have worked night shifts for more than 20 years, or work night shifts without daytime napping may have an increased risk of cancer, according to a study published in the Annals of Medicine.
The study carried out by the Huazhong University of Science and Technology in Wuhan, China, gathered data from interviews with middle-aged and older Chinese in the Dongfeng-Tongji Cohort Study, a group of approximately 27,000 retired workers from the Dongfeng Motor Corporation.
The researchers were investigating the effects three sleep habits on cancer incidence: Night shift work, daytime napping, and nighttime sleep.
The authors report that men who had worked night shifts for more than 20 years had a 27 percent increased risk of cancer incidence, and that men that did not nap in the daytime had double the risk of cancer of those who regularly took a 30-minute nap.
They also found that men who slept for more than ten hours per night had an increased risk of cancer. However, no such relationship was observed in women.
The researchers also found that male participants with at least two of these sleep habits had a 43 percent increased risk of cancer incidence and a two-fold increase in cancer mortality, compared to those who exhibited none of the sleep habits.
The researchers did note, however, that the age of the study participants, self-reported lifestyle data, and a short follow-up period to their study might limit their conclusions, and that a long-term study would be needed to verify their findings.