Insomnia doubles the risk of prostate cancer, study claims

Men who reported sleep problems, including difficulty falling asleep and staying asleep, had up to a twofold increased risk for prostate cancer, according to data published in Cancer Epidemiology, Biomarkers & Prevention, a journal of the American Association for Cancer Research.

"Sleep problems are very common in modern society and can have adverse health consequences," said Lara G. Sigurdardóttir, M.D., at the University of Iceland in Reykjavik. "Women with sleep disruption have consistently been reported to be at an increased risk for breast cancer, but less is known about the potential role of sleep problems in prostate cancer."

Previous studies have generated conflicting results for an association between sleep disruption from working night shifts and the risk for prostate cancer. Sigurdardóttir and her colleagues, therefore, investigated the role of sleep in influencing prostate cancer risk.

The researchers followed 2,102 men from the prospective Age, Gene/Environment Susceptibility-Reykjavik study, which involved an established, population-based cohort of 2,425 men aged 67 to 96. Upon enrollment into the study, the participants answered four questions about sleep disruption: whether they took medications to sleep, had trouble falling asleep, woke up during nights with difficulty going back to sleep or woke up early in the morning with difficulty going back to sleep.

Among the participants, 8.7 percent and 5.7 percent reported severe and very severe sleep problems, respectively. None of the participants had prostate cancer at study entry. The researchers followed the participants for five years, and during this period, 6.4 percent were diagnosed with prostate cancer.

After the researchers adjusted for age, they found that compared with men who reported no problems with sleeping, the risk for prostate cancer increased proportionately with reported severity of problems falling and staying asleep, from 1.6-fold to 2.1-fold. Further, the association was stronger for advanced prostate cancer than for overall prostate cancer, with more than a threefold increase in risk for advanced prostate cancer associated with "very severe" sleep problems.

Circadian disruption, sleep loss, and prostate cancer risk: a systematic review of epidemiologic studies

Disruption of the circadian system has been hypothesized to increase cancer risk, either because of direct disruption of the molecular machinery generating circadian rhythms or because of disruption of parameters controlled by the clock such as melatonin levels or sleep duration. This hypothesis has been studied in hormone-dependent cancers among women, but data are sparse about potential effects of circadian disruption on the risk of prostate cancer. This review systematically examines available data evaluating the effects of light at night, sleep patterns, and night shift work on prostate cancer risk.