Melatonin is a hormone that is produced exclusively at night in the dark and is an important output of the circadian rhythm, or the body's inherent 24-hour clock. Many biological processes are regulated by the circadian rhythm, including the sleep-wake cycle. Melatonin may play a role in regulating a range of other hormones that influence certain cancers, including breast and prostate cancers.
Sarah C. Markt, MPH, doctoral candidate in the Department of Epidemiology at Harvard School of Public Health in Boston and colleagues examined the association between urine levels of the main breakdown product of melatonin, 6-sulfatoxymelatonin, and risk of prostate cancer,
Researchers conducted a case-cohort study of 928 Icelandic men from the AGES-Reykjavik cohort between 2002 and 2009. The researchers were looking for urinary levels of 6-sulfatoxymelatonin, the main breakdown product of melatonin.
Researchers collected first morning void urine samples at recruitment, and asked the participants to answer a questionnaire about sleep patterns. Determination of prostate cancer diagnoses and mortality among men was obtained by linking the cohort to the nationwide Icelandic Cancer Registry and the Causes of Death Registry through 2009.
Among the study participants 111 men were diagnosed with incident prostate cancer, including 24 with advanced disease.
The results showed men who had reported sleep problems at baseline had lower 6-sulfatoxymelatonin levels compared to those who reported no sleep problems.
Men whose 6-sulfatoxymelatonin levels were higher than the median value had a 75% decreased risk for advanced prostate cancer. Overall, a 31% decreased risk for prostate cancer was found but was not statistically significant.
The researchers write “Higher urinary 6-sulfatoxymelatonin levels were associated with a decreased risk of prostate cancer, particularly advanced disease. These data provide support for the influence of the circadian rhythm in prostate carcinogenesis.”
"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," Markt said in a press 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.”
Even though the statistical link was strong, Market pointed out that the findings need to be reproduced in a larger sample size before any public health recommendations can be made.
"Further prospective studies to investigate the interplay between sleep duration, sleep disturbance, and melatonin levels on risk for prostate cancer are needed," said Markt.
These results were presented at the AACR-Prostate Cancer Foundation Conference on Advances in Prostate Cancer Research, held Jan. 18-21.
Prostate cancer is the most common type of cancer found in American men, other than skin cancer. Prostate cancer is the second leading cause of cancer death in men, behind only lung cancer. One man in 6 will get prostate cancer during his lifetime. And one man in 36 will die of this disease, according to the American Cancer Society.
Information on prostate cancer can be viewed online at the National Cancer Institute.