EnviroHealth Tutorial 10: Switching off is good for you

Most of us know by now that using less electricity is crucial to halting climate change, but switching off the lights may have other more direct health benefits too.

Your nightly dose of darkness
Sleep scientists now think that too much artificial light at night, which causes us to have an unnaturally extended day, may have various negative health effects.

Too much artificial light at night reduces production of the “sleep” hormone melatonin, disturbs the circadian rhythm (your body's internal clock that regulates the sleep-wake cycle), increases stress and suppresses the immune system.

We’re familiar with how disturbed sleep (caused, for example, by shining a bright light on a sleeper’s face) causes sluggishness, poor concentration, depression and irritability. But reduced melatonin might be a causative factor in serious health problems in the long term too.

Melatonin is thought to help protect genetic material from the mutations that lead to cancer. Thus artificially extended days, and the melatonin suppression this may cause, could increase the risk for certain cancers. Night-shift work has been officially classified as "probably carcinogenic”, and sleep scientists recommend that it should be limited to a maximum of two nights a week.
Studies on women who work the night shift have shown that their incidence of breast cancer increases, and it increases even more with longer shifts and the number of years they spend working at night. Evidence is mounting that the night shift predisposes workers to endometrial, prostate and colorectal cancer as well.

Scientists have also speculated that artificial light could have contributed to the increase in childhood leukemia – up by about 50% over the last (increasingly well-lit) fifty years.

“Precocious” puberty – when signs of puberty appear earlier than normal – is also increasing throughout the developed world, particularly among girls. One suspected factor is their average weight increase; another is reduced melatonin levels from too much artificial light.
Too much screen time also encourages children to be sedentary, making them more prone to overweight, which is thought to further suppress melatonin production. Decreased melatonin levels disturb sleep patterns and may cause hyperactivity.

And also worrying: children who used night-lights up to age two showed a significantly greater chance of developing short-sightedness.

How to get a good night’s dark:
  • Follow the dark-light sleep-wake cycle, as our ancestors did, by turning in early and rising with the sun. Make it your routine to get a full night's sleep in natural darkness. If you wake up during the night, aim to keep the lights off if possible.
  • Use blinds or curtains to block “light pollution” from street lights.
  • Rather don’t use night-lights for children, or wean them off these by gradually dimming the source or moving it away from the bedside. A nice green option for a nightlight is a “sun jar” or solar lamp: these charge up when you place them in sunlight during the day, then give out several hours of mellow light at night before gradually fading. And it won’t hurt to cut down on the time kids (and others) spend watching TV or surfing the internet.
  • If you do shift work, try to organise with your employer that you do fixed shifts rather than rotating shifts: the latter is thought to be far more disruptive to the sleep-wake cycle, and carries potentially higher health risks.
  • Even if you don't work the night shift, consider that studying, partying or watching TV till the small hours also exposes you to excessive amounts of artificial light.

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