Late-night exposure to light may diminish levels of a natural cancer-fighting hormone

Apr 5 2009

The answer may surprise you in that studies are finding that late-night exposure to light may diminish levels of a natural cancer-fighting hormone. Dr. David Blask, professor of the practice in the Tulane University School of Medicine Department of Structural and Cellular Biology, is a widely acclaimed expert on cancer biology, circadian rhythms and the health implications of exposure to light.

In the early 1980s, Blask was one of only a handful of scientists studying regulation of breast cancer development and growth by melatonin, a hormone produced by the pineal gland during sleep in the darkness of night. Melatonin modulates many of the body's natural circadian rhythms, including the sleep/wake cycle, and has been shown to have important anti-cancer properties.

He was the first to demonstrate that nighttime doses of melatonin suppress human breast cancer cell growth. He has become a world-renowned expert on the negative health implications and increased cancer risk associated with melatonin suppression due to exposure to light at night.

Using specially designed photoperiodic chambers, which allow precise control over light exposure at night, he and his research team have demonstated that manipulating light intensity at night, and thus melatonin production, dramatically affects human breast cancers growing in rats. Their experiments show that reduced levels of melatonin coupled with higher levels of light at night boosted human breast cancer tumor growth in rats.

This landmark research helped to lay the groundwork for a scientific working group (of which Blask was a member) appointed by the World Health Organization to add shift work and exposure to light at night to its list of possible carcinogens. Shift workers have been shown to have higher risks for breast, prostate and other cancers.

Blask has advised Congressional staffers on the implications of light pollution on the environment as part of an effort to get the Environmental Protection Agency to address the problem.

Blask is available to speak about the implications of shift work and cancer risk and ways people can minimize their risk when required to work late nights.