Men younger than 65 years who sleep less than six hours per night have an increased risk of death from prostate cancer, according to the results of a study presented at the American Association for Cancer Research 2017 annual meeting.

Researchers analyzed self-reported sleep data from 407,649 and 416,040 men in the Cancer Prevention Study-I and -II cohort studies, respectively. They found that men younger than age 65 who slept three to five hours per night had a 55% increased risk of dying from prostate cancer than men who slept seven hours per night. Men who slept six hours per night had a 29% increased risk compared to men who slept seven hours. They found no associations in men who were older than 65 years.

The researchers said that it was unclear why less sleep increased the risk, but they noted that impaired melatonin production and sleep disruption are linked to oxidative stress, gene mutations, impaired DNA repair, immune suppression, and dysregulation of tumor-suppressor genes. They said their findings add to evidence that circadian rhythms are involved in prostate carcinogenesis.