Light at Night Risk for Breast Cancer

Sep. 30, 2002 (Ivanhoe Newswire) -- Researchers found light at night may be associated with an increased risk in breast cancer. Richard G. Stevens, Ph.D., from the University of Connecticut Health Center, presented his findings this week at the "Era of Hope" Department of Defense Breast Cancer Research Program meeting in Orlando, Fla.

Stevens says electromagnetic fields released by light suppress the normal nocturnal production of melatonin, which could increase the release of estrogen by the ovaries. He says this would explain why industrialized societies have five times the risk of breast cancer.

Stevens and his colleagues examined the association between light and breast cancer risk in 800 healthy women and 800 women with breast cancer in Seattle. Researchers gathered information on sleep habits and bedroom lighting in the 10 years before diagnosis and lifetime occupational history. Results show a slight increase in risk for women who frequently did not sleep during the period of the night when melatonin levels are typically at their highest. There was an indication of increased risk among women with the brightest bedrooms. Graveyard shiftwork was also associated with increased breast cancer risk, with a trend of increased risk with increasing years and with more hours per week of graveyard shiftwork.

Previous studies show slight increases of breast cancer risk for flight attendants and rotational shift nurses, but half the risk for blind women. Stevens suggests researchers also examine restaurant workers and women who work in photography dark rooms. In addition, he says researchers should study light effects on mammary tissue in rats. Though several studies show low or no associations between electromagnetic fields and breast cancer risk, Stevens and fellow panelists at the meeting agree there is not a lot of concrete evidence and many questions remain.

The Department of Defense Breast Cancer Research Program meeting is for breast cancer survivors, military, scientists and physicians to meet and discuss the latest advances in breast cancer research.