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New findings suggest that more care should be taken in considering the amount of light exposure people get.
Too much light is bad for your health. So suggests research in mice, which found that six months of continuous lighting led to a
loss of strength and bone mass, and signs of increased inflammation. The findings are worrying for people who experience prolonged light exposure - such as shift-workers and hospital patients - but
some of the effects seem to be reversible.
The experiment involved 134 mice, which experienced no dark for half a year. By the end, the mice had lost about half their strength compared with controls, as measured by grip endurance tests and their ability to cling to bars, while the signals of their internal body clocks were weakened.
Their bones were affected too. The bulbous, spongy parts of their bones that are responsible for bearing most weight
lost a third of their volume, and became 10 per cent thinner - just as in the early stages of osteoporosis.
There were also signs of
increased inflammation, such as a rise in the number of neutrophil white blood cells - usually associated with stress or infection.
Comment: Any exposure to nighttime light suppresses our body's production of melatonin which regulates our sleep-wake cycle. Melatonin lowers blood pressure, glucose levels, and body temperature - key physiological responses responsible for restful sleep. At the same time, artificial lighting
unnaturally elevates cortisol levels at night, which disrupts sleep and can cause insulin resistance and systemic inflammation. Chronic exposure to even dim light at night has been linked to depression, premature aging and heart problems.
Comment: The majority of physiologic processes in the human body are regulated by light cycles and circadian rhythms. Neural tracts in the central nervous system are wired to respond predominantly to light signals received by receptors in the eye and surfaces including the skin, the lungs, and the GIT tract. Exposure to artificial light after sunset causes the body to function like it would in daytime, thereby creating a 'mismatch' in physiological signalling. See the following: