Bones, muscles, immune system: all are negatively affected by permanent exposure to artificial light. This is the result of a study on mice.
Light sources are omnipresent in a home: the Internet box, the clock radio and the television are all devices that emit a slight light at night. Not to mention the lampposts, which let a glow pass through the curtains or shutters. This permanent exposure to artificial lighting seems rather harmful to our health. A study on the mouse, published in Current Biology, reports a very broad effect on the functioning of the body.
Osteoporosis, inflammation …
75% of the population live permanently under artificial light. The impact of this exhibition is still poorly understood. But more and more scientific work suggests that it harms the body. For the study property, a group of rodents was subjected to such conditions for 24 weeks. The researchers, from the University Hospital of Leiden (Netherlands), monitored various indicators of animal health throughout this period.
The brain activity of mice is altered when darkness is not total. A region responsible for regulating the circadian rhythm is slowed down by 70%, the suprachiasmatic nucleus. This disturbance is reflected, in the different specimens, by pro-inflammatory activation of the immune system, muscle and bone loss. They thus presented early signs of osteoporosis. These frailty indicators are generally observed with age.
A reversible effect
For Johanna Meijer, co-author of the study, these results are not a real surprise: life on Earth has evolved in a rhythm of alternation between light and dark. “We have optimized our body to live according to cycles,” she sums up. But the flip side is that we are affected by the lack of such cycles. “
However, these effects can be resolved in a very simple way: by restoring a strict alternation between light during the day and total darkness at night. Subjected to this rate for two weeks, the mice saw their general health improve.
These results are important in view of the proportion of the population regularly exposed to partial penumbra. In addition to people who live in cities, night workers also suffer the consequences of this lack of alternation. In France, they are around 3.5 million.
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