Decreased Melatonin Production Linked to Light Exposure

By Tillett, Tanya | Environmental Health Perspectives, February 2006 | Go to article overview

Decreased Melatonin Production Linked to Light Exposure


Tillett, Tanya, Environmental Health Perspectives


Decreased Melatonin Production Linked to Light Exposure

Blask DE, Brainard GC, Dauchy RT, Hanifin JP, Davidson LK, Krause JA, et al. 2005. Cancer Res 65(23):11174-11184.

The incidence of breast cancer is up to fives times higher in women living in industrialized nations compared to those living in developing countries, and female night shift workers have particularly high rates of the disease. Given that Western nations have become "24-hour societies," with more people awake around the clock, one hypothesis holds that nighttime exposure to artificial light suppresses the nocturnal production of melatonin. This hormone, produced by the pineal gland, helps regulate the body's circadian rhythm and immune function, and also suppresses tumor growth. Now NIEHS grantees David E. Blask and George C. Brainard and their colleagues have confirmed that ocular exposure to bright artificial light at night inhibits the production of melatonin, which in turn may lead to an increased risk of developing breast cancer.

The researchers implanted human breast cancer cells into female laboratory mice, then transferred the malignant tumors that formed to female rats for continued development. They then collected blood from several healthy premenopausal volunteers under three different conditions: during the day, during the night following two hours of complete darkness, and during the night following 90 minutes of exposure to bright fluorescent light. …

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