Lighting innovations prevent disease.

• Position: Biological Clock

"New discoveries about lighting and human health--its impact on breast cancer and Alzheimer's, for example--make us predict that the way we light our offices, homes, and factories will be subject to massive change," theorizes John R Bachner. communications director of the National Lighting Bureau, a not-for-profit information resource funded by private industry, professional societies trade associations, and agencies of the Federal government.

"Up to now," Bachner continues, "lighting has been designed almost exclusively to support visual needs. A growing body of research tells us that lighting can do far more than help us see, however. As we learn more, new lighting system components will be created not only to enhance our visual performance, but to help prevent disease as well."

Many of light's health effects stem from its ability to influence circadian rhythms, 24-hour oscillations in neural activity controlled by a "master biological clock" located in the suprachiasmatic nucleus (SCN) of the hypothalamus. Recently discovered nonvisual photosensitive retinal ganglion cells (RGCs) connect directly from the retina to the SCN, and influence the secretion of melatonin by the pineal gland. Melatonin acts somewhat as an antioxidant "blood cleaner" as its levels build up while we sleep. Light inhibits melatonin production at night, and research shows that women who work during late shifts are far more susceptible to breast cancer.

"The logical conclusion," Bachner indicates, "is that those who work at night need to use light--and the absence of light--to create a virtual normal' light-dark cycle."

Light also is associated with the production of vitamin D--the sunshine vitamin--a hormone that, in some forms (D3), is manufactured in the skin when light strikes it. Researchers suggest that people are obtaining less vitamin D3 because they have reduced their exposure to sunlight in order to avoid skin cancer. In a Finnish...