Low Melatonin Associated with Increased Risk of Breast Cancer in Postmenopausal Women

Melatonin is primarily secreted during the dark hours of a light-dark cycle and has been shown to be low in some night workers. Researchers have found that low melatonin levels in premenopausal women are associated with an increased risk of breast cancer.

To find out if a similar association occurs in postmenopausal women, Eva Schernhammer, M.D., Dr.P.H., of the Brigham and Women's Hospital and Harvard Medical School in Boston and colleagues compared melatonin levels in 178 postmenopausal women and 710 matched controls. All of the women were enrolled in the prospective Hormones and Diet in the Etiology of Breast Cancer Risk study.

The researchers found that women with the lowest levels of melatonin had a statistically significantly higher incidence of breast cancer than those with the highest levels.

The researchers conclude that low melatonin levels are associated with an increased risk of breast cancer. Further studies need to confirm these data and should investigate the mechanisms that underlie the association.

This research was recently published in the Journal of the National Cancer Institute.