New research from the Harvard School of Public Health in Boston suggests that higher levels of melatonin, a hormone involved with the sleep-wake cycle, is associated with the lower risk of advanced prostate cancer.

"It's notable that we found a stronger association between melatonin levels and more advanced prostate cancer," said study researcher Sarah Markt, a doctoral candidate in the department of epidemiology at the Harvard School of Public Health in Boston.

Melatonin, produced in the brain’s pineal gland at high levels during night relative to the daytime, is known for the role in regulating the sleep-wake cycle. According to Markt, there have been previous experiments that show melatonin have anti-carcinogenic properties, with the ability to slow down and even stop cancer growth and proliferation.

The study also found that men with higher levels of the melatonin breakdown product, called 6-sulfatoxymelatonin, in their urine had a 75 percent less chance of developing advanced prostate cancer, compared to men with lower melatonin levels.

The case-cohort study examined morning urine samples from 928 men from Iceland, between the years 2002 to 2009. They collected first morning urine samples at recruitment, and asked the participants to answer a questionnaire about sleep patterns. One in seven men reported problems falling asleep, one in five men reported problems staying asleep, and almost one in three reported taking sleeping medications.

When the researchers looked to see how many of the men developed prostate cancer through 2009, 111 men in the study developed prostate cancer, with 24 cases of advanced prostate cancer. They also establish an association between having 6-sulfatoxymelatonin urine levels above the median level and a 31 percent decreased risk of overall prostate cancer. The association is borderline statistically significant.

This research is alarming for individuals who work well into the evening or is surrounded by light at night. Markt told HuffPost, that "the literature suggests there are differences in the amount of melatonin produced between individuals; however, melatonin production may be suppressed through light exposure."

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http://www.aacr.org/home/public--media/aacr-in-the-news.aspx?d=3260