Sound Sleep Linked to Reduced Risk of Prostate Cancer

Higher levels of the hormone melatonin, which plays a key role in regulating sleep and wake cycles, lower the risk of developing advanced prostate cancer, claims a new finding.

The case cohort study conducted on 928 Icelandic men revealed that men with higher levels of sleep hormone, melatonin, in their urine had a 75 percent reduced risk of developing advanced prostate cancer, the second leading cause of death among American men.

Secreted by the pineal gland, melatonin, a hormone that is found naturally in the body, helps control the internal clock. Generally, it is during the mid-to late evening that levels of melatonin begin to rise. The levels of the hormone drop during the early morning hours. Also the levels drop along with advancing age.

Extremely small amount of this hormone is present in fruits, vegetables, meat and grains. Apart from this, the hormone regulates other hormones and maintains the body's circadian rhythm. It is also an antioxidant and is prescribed by doctors to those with sleep problems.

"Sleep loss and other factors can influence the amount of melatonin secretion or block it altogether, and health problems associated with low melatonin, disrupted sleep, and/or disruption of the circadian rhythm are broad, including a potential risk factor for cancer," said Sarah C. Markt, M.P.H., doctoral candidate in the Department of Epidemiology at Harvard School of Public Health in Boston.

It was seen that men with higher levels of melatonin had a 75 percent lower risk of developing prostate cancer compared to men with lower levels of this hormone.

Markt states that the study requires replication. But it supports the significance of maintaining a stable light/dark and sleep/wake cycle. Since the levels of melatonin can be modified, it is necessary to conduct further studies exploring the link between melatonin and risk of prostate cancer.

The researchers worked on the data of 928 Icelandic men that were a part of the AGES-Reykjavik cohort between 2002-2009. As a part of the analysis, the first morning void urine samples of the subjects were collected and they were asked to complete a questionnaire that included questions on their sleep patterns.

On analyzing the data, the researchers noticed that one in seven men reported having problems falling asleep, one in five reported having problems staying asleep and one in three claimed to consume sleeping medications.

On examining the link between urine levels of the main breakdown product of melatonin, 6-sulfatoxymelatonin, the researchers noted that the median value of 6-sulfatoxymelatonin in the subjects was 17.14 nanograms per millimeter of urine. Lower levels of 6-sulfatoxymelatonin were seen in men taking medications and having sleep problems compared to men without any such problems.

On the whole, 111 men had developed prostate cancer along with 24 advanced disease. The researchers state that men with higher levels of melatonin had a 75 percent reduced risk of prostate cancer.

"Further prospective studies to investigate the interplay between sleep duration, sleep disturbance, and melatonin levels on risk for prostate cancer are needed," said Markt.

The study was presented at the AACR-Prostate Cancer Foundation Conference on Advances in Prostate Cancer Research.