Higher Melatonin Levels Associated With Lower Prostate Cancer Risk

Having higher levels of the hormone melatonin is associated with a lower risk of advanced prostate cancer, according to a new study.

Melatonin is known for its role in regulating the sleep-wake cycle, and is naturally produced by the body's pineal gland during darkness. Melatonin levels stay high during the nighttime, and then fall during the daytime.

Previous experimental studies have shown that melatonin has anti-carcinogenic properties, with the ability to reduce cancer cell proliferation and stop cell cycle progression, study researcher Sarah C. Markt, M.P.H., a doctoral candidate in the Department of Epidemiology at Harvard School of Public Health, told HuffPost. In addition, other epidemiological studies have shown evidence that melatonin could help reduce risk of other cancers, including breast cancer.

She noted that there are three interrelated pathways that may have an effect on cancer risk: disrupted melatonin, disrupted sleep, and disrupted circadian rhythm. The new study -- where it was found that men with higher levels of the breakdown product of melatonin in their morning urine, called 6-sulfatoxymelatonin, had a lower risk of developing advanced prostate cancer -- seems to provide "further support for the influence of the circadian rhythm in prostate carcinogenesis," Markt said.

For the study, researchers analyzed the morning urine samples from 928 men from Iceland who were part of the AGES-Reykjavik cohort from 2002 to 2009. All the participants also answered questionnaires about their sleep, which revealed that one in five men had trouble staying asleep, one in seven men had trouble falling asleep, and one in three men took sleeping medications.

Then, researchers looked to see how many of the men developed prostate cancer through 2009. A total of 111 men developed prostate cancer, with 24 of the cases being advanced prostate cancer.

They found an association between having 6-sulfatoxymelatonin urine levels above the median level of 17.14 nanograms per milliliter of urine, and a 31 percent decreased risk of overall prostate cancer, though the association was only borderline statistically significant.

However, the researchers did find that "men with higher 6-sulfatoxymelatonin levels had a 75 percent significantly reduced risk of advanced disease compared to men with lower levels," according to the study abstract.

Markt explained that "the literature suggests there are differences in the amount of melatonin produced between individuals; however, melatonin production may be suppressed through light exposure." In other words, if someone is exposed to light during a time when the body is naturally producing melatonin, production of melatonin will immediately stop. Many factors can affect the secretion of melatonin, including exposure to light at night, certain drugs (such as beta-blockers) and shift work.

The findings were presented at the AACR-Prostate Cancer Foundation Conference on Advances in Prostate Cancer Research; because they have yet to be published in a peer-reviewed journal, the findings should be regarded as preliminary.