The Health Benefits of LED Lighting
Joseph R. Knisley | Electrical Construction and Maintenance | Dec. 18, 2012
Abstract:
LEDs are also showing general health benefits for humans. An LED is made like other semiconductor products, with each diode being cut from a wafer of crystals layered over a base of silicon, sapphire, nitride, or some other material. The crystal layer on early LEDs was gallium arsenide or gallium phosphide, which produces a narrow band of red color. All other colors, such as green, blue, or amber, also depend on the semiconductor materials used to make the diode.
Because LEDs emit light at precise wavelengths — that is, where a specific spectral composition of light is important — they are ripe for medical/health benefit applications. We are just at the threshold of understanding how light levels and colors affect people — the intricacies of the interaction between lighting and our circadian rhythms.
When we don’t receive a strong, regular reception of light (similar to daylight), our “body clock” malfunctions. If a lighting control system can adjust the spectral content of light as well as the light level throughout the day, imitating the daylong presence of sunlight, it can help our biological clock, or circadian rhythm, stay in sync. During the central part of the day, blue light, at about 460 nm, stimulates hormone production for alertness and activity. Later in the day and evening, warmer color temperatures are preferred to help in the production of melatonin, the hormone secreted from the pineal gland that is needed for sleep activity.
A majority of older adults report experiencing problems with sleep, and the LED light source can assist in providing the optimum amount of light and preferential wavelengths for people throughout the day. A 2008 study, with subjects whose average age was 85.5, demonstrated improvements in depression, agitation, and sleep when they received high daytime levels of light — plus or minus 92 fc. The ANSI/IES RP-28-07 document, “Lighting and the Visual Environment for Senior Living,” has recommendations for the aging population. However, they only apply for vision.
In 1980, The National Institute of Mental Health (NIMH) discovered the connection between light and health in an experiment that demonstrated how bright white light could suppress melatonin production. A few years later, scientists demonstrated that circadian rhythms in humans could be disrupted. In 2001, Dr. George C. Brainard, a professor of neurology in the Jefferson Medical College at Thomas Jefferson University, found that circadian rhythms could be disrupted with fairly low levels of blue light. He and other researchers concluded that the eye must have photoreceptors sensitive to blue light that perform non-visual functions. This hypothesis was confirmed a year later, when researchers at two institutions physically isolated the receptor.
Complete: ecmweb.com
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