Bright Lights and Breast Cancer

Simon and Garfunkel's "Hello darkness, my old friend" has taken on new meaning with reports of a study that women exposed to bright noctural lighting have higher breast cancer rates than those who spend their nighttime hours in unlit surroundings.

By overlaying satellite images of Earth on geographical reports of cancer, Israeli scientists tested the hypothesis that exposure to excessive light at night can raise the risk of breast cancer by interfering with the brain's production of a tumor-suppressing hormone. They found "a clear and strong correlation."

Previous studies of nurses, flight attendants and other night workers found breast cancer rates 60 percent above normal. As a result, the World Health Organization recently classified their work as a "probable carcinogen," putting the night shift in the same health-risk category as exposure to toxic chemicals.

Scientists believe melatonin, which the body produces primarily at night, may be the answer. Levels drop sharply in the presence of light in that part of the spectrum emitted by computer screens and fluorescent bulbs.

Now that the risk has been identified, the search for ways to minimize or eliminate it can begin.