Link Between Melatonin & Prostate Cancer

Melatonin is a hormone that is produced at-night in the dark and is an important output of the circadian rhythm, or the body's internal clock. Many biological processes are regulated by the circadian rhythm, including the sleep-wake cycle. Sarah C. Markt, from the Harvard School of Public Health (Massachusetts, USA), and colleagues investigated the association between urine levels of the main breakdown product of melatonin, 6-sulfatoxymelatonin, and risk of prostate cancer, The team conducted a case-cohort study of 928 Icelandic men from the AGES-Reykjavik cohort between 2002 and 2009. They collected first morning void urine samples at recruitment, and asked the participants to answer a questionnaire about sleep patterns.  The researchers found that 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. The median value of 6-sulfatoxymelatonin in the study participants was 17.14 nanograms per milliliter of urine. Men who reported taking medications for sleep, problems falling asleep, and problems staying asleep had significantly lower 6-sulfatoxymelatonin levels, as compared with men without sleep problems. Of the study participants, 111 men were diagnosed with prostate cancer, including 24 with advanced disease. The researchers found that men whose 6-sulfatoxymelatonin levels were higher than the median value had a 75% decreased risk for advanced prostate cancer.