City dwellers are used to public lighting at night. This artificial lightubiquitous in everyday life could disrupt the circadian rhythm and affect human health. Dutch researchers claim that this overexposure to unnatural light could be responsible for a loss of bone density.
The experience reported in Current biology was carried out in mice under extreme conditions: neuroscientists Eliane Lucassen and Johanna Meijer, from the University of Leide in the Netherlands, implanted electrodes in the parts of the brain that control the circadian rhythm(the biological clock that governs the sleep-wake cycle) to observe neuronal activity in rodents. The young guinea pigs were exposed for six months to harsh artificial light.
As a result, the mice showed a loss of bone density associated with muscle weakness. These symptoms disappeared as soon as the rodents were able to regain periods of darkness.
Night workers more at risk
If this study was conducted on mice, the researchers still see a danger to the bones, hitherto ignored, of night work or shift work – lifestyles that disrupt the biological clock.
The health effects of night workare regularly singled out. In particular, they increase the risk of obesity, type 2 diabetesand cardiovascular disorders.
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