MONDAY, Jan. 20, 2014 (HealthDay News) -- A link may exist
between the sleep hormone melatonin and prostate cancer, according
to a new study. But experts say it's too early for men to start
popping melatonin supplements to help prevent the disease.
Results of the study, which included 928 Icelandic men, suggest
men who have higher levels of melatonin may have a lower risk of
developing prostate cancer, said lead author Sarah Markt, a
doctoral candidate in the department of epidemiology at Harvard
School of Public Health.
"Men who had higher levels of melatonin had a 75 percent reduced risk for developing advanced prostate cancer compared with men who had lower melatonin. The risk was especially reduced when it came to advanced disease," Markt said.
The research was scheduled for presentation Sunday at an
American Association for Cancer Research meeting focused on
prostate cancer, held in San Diego.
Melatonin is believed to be connected with the body's circadian
rhythms, Markt said, although it isn't necessarily produced during
sleep. The hormone is secreted by the pineal gland during the
night, and represents the biochemical signal of darkness, she
She was interested in studying a potential link between
melatonin levels and prostate cancer because a number of other
studies have suggested that low melatonin and disrupted sleep can
be related to health problems, including a potential risk for
"In experimental studies -- animal studies and prostate cancer cell lines -- it's been shown that melatonin has an inhibiting effect on prostate tumor growth," Markt said.
She and her colleagues analyzed data from a 2002 to 2009 study
of Icelandic men. The investigators used urine samples from
participants to measure melatonin levels and linked them to cancer
and death registries. The men also answered a questionnaire about
One in seven men reported problems falling asleep, one in five
men said they had problems staying asleep, and about one in three
reported taking medication to help them sleep, the study found. Men
with sleep troubles had significantly lower levels of the chemical
6-sulfatoxymelatonin -- a breakdown product of melatonin --
compared to men who reported no sleeping issues.
Of participants, 111 men were diagnosed with prostate cancer,
including 24 with advanced prostate cancer, researchers
Although the study found an association between melatonin levels
and prostate cancer risk, it did not prove a cause-and-effect
relationship, and experts noted that other factors might be
June Chan, a professor of epidemiology, biostatistics and
urology at the University of California, San Francisco, who was not
involved with the study, said the findings are provocative and
merit further confirmation and study.
"The association between melatonin and cancer has been observed in other cancer types as well," Chan said, adding that reports date back as far as 1970, and include breast cancer studies.
She added that research would need to rule out other potential
risk factors that track with melatonin, such as exercise, and
vitamin D levels. "I think these data are pretty early to suggest
that men should take melatonin supplements solely for prevention of
prostate cancer," Chan said.
Dr. Stephen Freedland, an associate professor of urology and
pathology at Duke University, said the study concept is plausible,
but he added that the fact that the men in the study come from a
place with light extremes might also affect results.
"One confounding factor is that these are men in Iceland," Freedland said. "They spend practically six months of the year with no sunlight and six months with sunlight. What time of year was this done? There's actually data that suggest sunlight may be good for prostate cancer."
Study author Markt agreed that the results are not conclusive.
"Prospective studies to investigate the interplay between sleep
duration, sleep disturbance and melatonin levels on the risk for
prostate cancer are needed," she said.
Because this study was presented at a medical meeting, the data
and conclusions should be viewed as preliminary until published in
a peer-reviewed journal.
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