Melatonin is a hormone that is produced only at night and is key in regulating the body's circadian rhythm; new research suggests it could work to regulate other hormones that have been linked to conditions such as breast and prostate cancer.
"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," Sarah C. Markt, M.P.H., doctoral candidate in the Department of Epidemiology at Harvard School of Public Health, said in an American Association for Cancer Research news release. "We found that men who had higher levels of melatonin had a 75 percent reduced risk for developing advanced prostate cancer compared with men who had lower levels of melatonin."
The link is believed to be strongly associated with the circadian rhythm, which is the body's 24 hour "sleep-wake" cycle.
"Our results require replication, but support the public health implication of the importance of maintaining a stable light-dark and sleep-wake cycle," Markt said. "Because melatonin levels are potentially modifiable, further studies of melatonin and prostate cancer risk and progression are warranted."
The researchers conducted a case-cohort study that looked at 928 Icelandic men. They took urine samples from the participants and asked them to fill out a questionnaire on their sleeping patterns.
One in seven of the men reported they had trouble falling asleep at night while one in five had issues staying asleep. One in every three participants took sleep medications.
The team looked at levels of 6-sulfatoxymelatonin (a "breakdown product" of melatonin) in the study subjects' urine. The median concentration was found to be 17.14 nanograms per milliliter of urine. Those who reported sleep troubles or took sleep medications had significantly lower 6-sulfatoxymelatonin levels than men who had a healthy sleeping schedule.
Out of the participants 111 of the men were diagnosed with prostate cancer, 24 of which were considered to be an "advanced disease."
The team found those with 6-sulfatoxymelatonin levels that were higher than the median had a 75 decreased risk of advanced prostate cancer. They also found it decreased prostate cancer risk by 31 percent, but these findings were not "statistically significant."
"Further prospective studies to investigate the interplay between sleep duration, sleep disturbance, and melatonin levels on risk for prostate cancer are needed," Markt said.
