The Bright Side of Darkness: A better night's sleep and avoiding a caner risk
By Richard L. Hansler, PhD

Bright Light, Big Cancer” (Science News Online, January 7, 2006) and “The Light-Cancer Con-nection” (Prevention Magazine January 2006) are titles of recent articles that warn of the danger of using artificial light at night. Warnings actually go back to the 1990s when scientists discovered that blind people have only half the risk of cancer as do their sighted counterparts. There is not only the epidemiological evidence – such as the increased incidence of breast cancer in nurses working night shifts – but there is also experimental evidence from many studies conducted with animals that show a correlation between artificial light and cancer. In this study tumors grew rapidly in animals that were raised with short nights (more artificial light) while tumors did not grow (or grew slowly) in animals raised with long nights (less artificial light).

Using light at night may be hazardous to one's health due to nerves that run from special sensors in the retina of the eye that are connected to the pineal gland. The pineal gland produces melatonin, an important cancer-fighting hormone produced only when the eyes are in darkness. Melatonin is a powerful antioxidant that counteracts the damaging effects of free radicals produced by radiation and chemical pollutants. Melatonin also blunts the cancer-promoting nature of estrogen, and interferes with the metabolism of materials that feed cancer cells.

By shortening the length of time we spend in darkness, the length of time that melatonin is produced and present in the blood is reduced. Studies show that primitive societies that experience longer periods of darkness due to the absence of artificial lighting show a much lower incidence of cancer. Of course, there are other variables when comparing sophisticated nations and primitive cultures, but mounting evidence shows a correlation between the use of artificial light and increased health risks.

Without artificial light every place on earth would, on average, experience 12 hours of darkness each night. Recent studies at Harvard found that blind people (who are always in darkness) produce melatonin for 9-10 hours a night. Sighted people who were kept in darkness produce melatonin for the same period of time. Thanks to artificial lighting, most Americans are in darkness for only 7-8 hours a night, reducing their melatonin production time to only 6-7 hours each night. As mentioned previously, blind people have a 50 percent less risk of developing cancer.

It should be noted that melatonin is not the only hormone produced by the pineal gland. Pineal-gland production is more complex and includes other secretions. It is yet to be determined whether these secretions also play a significant role in fighting cancer. This may be why simply taking melatonin orally does not appear to be as effective as the body's making its own.

A definitive experiment recently was completed by highly experienced scientists, Dr. George Brainard, a neurology professor and the director of the Light Research Group at Thomas Jefferson University in Philadelphia, Dr. David Blask, a researcher at the Bassett Research Institute in Cooperstown, NY, and their associates. They examined blood drawn from women under three different conditions: during the day when melatonin was not present in the blood, during the darkness of night when melatonin was present and during the night when the women had been exposed to several hours of light. Melatonin was not present in the last group of women. In another phase of the research this blood was then supplied to human breast tumors growing on rats. This resulted in the tumors growing rapidly. Supplying the tumors with blood with melatonin resulted in slower growth or none at all. Dr. Blask commented that melatonin-rich blood, “put the tumors to sleep.”

What can be done with this knowledge? Since it seems unlikely that we will not soon give up using electric lights, it is especially encouraging to know that about five years ago it was discovered that not all spectrums of light suppress melatonin production. Only light in the blue end of the visible spectrum causes suppression, so blocking the blue light alleviates the problem. In practical use, other “colors” of light are okay to use for reading, watching television or working on a computer. This dynamic was first demonstrated at the University of Toronto when subjects working a simulated night shift wore goggles that blocked the blue light. The subjects continued making melatonin even though they were in brightly-lit surroundings.

The Lighting Research Institute at John Carroll University in Cleveland, Ohio, has developed light bulbs of various types with coatings that block blue light. There also are filters for television and computer screens and even eyeglasses that block the melatonin-suppressing blue light. People can wear these glasses a few hours before bedtime. Combining this “virtual darkness” with darkness experienced during sleep, the 9-10 hours of melatonin flow may be obtained that, hopefully, will reduce the risk of cancer.

There is another huge extra benefit to blocking blue light. Not only is melatonin a cancer-fighting hormone, it also is the sleep hormone. Melatonin in the blood makes us drowsy and wanting to drop off to sleep. Wearing glasses that block blue light a few hours before bedtime allows melatonin to be present in quantity at bedtime. Sleep comes very quickly, and people who have used the glasses report sleeping more. With 46 million prescriptions written last year for sleeping pills, the use of blue-blocking glasses may be a better method of treating insomnia, without the harmful side effects that drugs can cause.

Dr. Hansler graduated from the University of Chicago and received a Ph.D. in physics from Ohio State University. Since his retirement from GE in 1996, he has served as the director of the Lighting Innovations Institute at John Carroll University. He also is the executive director of the Light and Health Foundation. For more information, please visit www.sleepglasses.com, www.lowbluelights.com or www.lightinginnovations.net. Dr. Hansler may be reached by calling (216) 397-1657 or e-mailing rhansler@jcu.edu.