KARACHI Late-night shift work may increase the risks of developing cancer, says a new study.

According to Tulane University expert Dr. David Blask, late-night exposure to light may diminish levels of a natural cancer-fighting hormone.

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 bodys 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.

Now, in the latest study, using specially designed photoperiodic chambers, which allow precise control over light exposure at night, he and his research team have demonstrated that manipulating light intensity at night, and thus melatonin production, dramatically affects human breast cancers growing in rats.

The research teams experiments show that reduced levels of melatonin coupled with higher levels of light at night boosted human breast cancer tumor growth in rats.