​Keeping the lights on could make you sick

Health, it is increasingly turning out, isn’t just about eating green things and running the sorts of distances that leave the feet numb and angry. And smelly. Being healthy is about everything. Really, every single thing that can affect you has to be managed. Exhausting.

The latest enemy of good health and longevity is light. Well, artificial light. The sun might fire cancer into your cells, but its artificial replacement comes with its downsides.

This is according to new research published in the journal Current Biology last week (July 14). The team testing the mice in this particular experiment were from Leiden University Medical Centre in the Netherlands.

Mice are often used as a good replacement for humans. Because people don’t mind mice being gradually driven insane, where similar treatment to humans might raise a few eyebrows.

The mice were kept under conditions of constant light for months on end, fast-forwarding the effects that living at night under artificial lighting could have on a human over a lifetime.

Critically, the team found that removing the natural light-dark cycle is bad for the health of mice. And, by inference, humans. Researcher Johanna Meijer wrote: “We showed that the absence of environmental rhythms leads to severe disruption of a wide variety of health parameters.”

This disruption leads to what the team describes as best resembling an early onset of “frailty” – that thing that makes old people look that bit slower and less altogether.

The Leiden University team said this was because the light speeded up the things that add to ageing – such as muscle loss, early signs of osteoporosis (brittle bones) and inflammation of the immune system. The last bit is something that normally only happens when bad things – such as pathogens – attack the body.

But there is good news. When the mice were returned to a normal light-dark cycle for two weeks, they returned to their original healthy state. Meijer wrote: “The good news is that we subsequently showed that these negative effects on health are reversible when the environmental light-dark cycle is restored.”

That sort of a solution isn’t useful in a world where any daylight hours are spent producing x-number of economic units, and any eating or fun has to be achieved at night, under artificial light. Except to suggest that maybe dimming the lights or going to sleep earlier is a good idea.

Where the research is important is for people that work night hours in floodlit offices, and in nursing homes and intensive care units where patients are constantly exposed to light. Until now, the researchers said this light was seen as benign. Now facilities will have to start thinking about how they use light.

But it is a discussion that the researchers said humanity at large needs to have. The body evolved to function optimally with a natural cycle of light and darkness. Humans have overcome that natural restriction. Meijer wrote: “We seem to be optimised to live under these cycles, and the other side of the coin is that we are affected by a lack of such cycles.”

Sipho Kings
Sipho is the Mail & Guardian's News Editor. He also does investigative environment journalism.
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