Physiological effects linked to overexposure of artificial light
Since creation, life on Earth has been ruled by a 24-hour cycle of light and dark. However the revolutionary discovery of electric light turned night into day at the flick of a switch. Perhaps our bodies may not have been ready for this.
Recent findings say modern life, oscillating around insufficient exposure to natural light at day and excessive exposure to artificial light at night, can confuse body’s natural sleep pattern.
A recent study at the University of Connecticut has shown the link with artificial light exposure and disruption of circadian rhythms. The circadian system harmonizes body’s physiological function from digestion to body temperature maintenance and cell repair to immune reaction, with a 24-hour cycle of light and dark. Recently scientists have showed that certain cells in retina, sensing light, signals the presence or absence of light rather than conveying visual detail to brain. Action in these cells sets off a reaction calibrating clocks in every cell in a body. These cells are particularly sensitive to wavelengths of blue light, available in a daytime sky. However artificial lights, typically LCDs, some LEDs, and fluorescent bulbs, also favour blue side of the spectrum thereby suppress the sleep-inducing hormone melatonin. Therefore even a short exposure to these lights at night can trigger a night-subdued circadian system to behave as if day has arrived. Circadian disruption leads to altered light-triggered hormone release which in turn is linked with an array of health hazards ranging from obesity, depression, diabetes and even cancer.
Experts suggest using better and more circadian-friendly lighting: lights of dimmer and longer wavelengths, and avoiding the bright blue light of e-readers, tablets and smart phones. They recommend a general awareness of how our physiology is affected by the type of light emitted from these devices. A recent study showed delayed melatonin onset in people using e-readers to those who read old-fashioned books. Newer technologies is now making it possible to generate, direct, and manage light at night to better accommodate the circadian physiology of life forms.
The findings have been published recently in an invited article in the British journal, Philosophical Transactions of the Royal Society B.
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