Light vs sleep

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Why does light affect sleep?


Melatonin is the hormone that promotes sleep. It’s the tick and tock behind the body clock, controlling the day-night cycle by triggering an almost irresistible urge to snooze.

When less light enters the eye, melatonin is produced in the brain, which brings on a desire to sleep. So for tens of thousands of years, sunset’s lower light levels told people’s body clocks that it was time for bed.

Then came Thomas Edison and the electric light bulb.

Followed by the LED television, the smartphone, the tablet, the e-reader… Over the course of 125 years, our lives became illuminated in all sorts of new ways.


How modern technology has reset our body clocks


For lots of us, the sun is just one of many different light sources. In fact, a typical day could easily start before sunrise with checking a backlit smartphone and watching an LED television.

And who goes to bed at sunset?

Huge numbers of us spend our evenings on smartphones, computers, tablets and e-readers. All of these devices feature backlit displays that are playing havoc with our body clocks.

  • Normal indoor lighting delays melatonin production at night by 90 minutes
  • Men exposed to fluorescent bulbs produce 40% less melatonin in a day
  • Using e-readers makes it harder to fall asleep
  • Two hours on a tablet suppresses melatonin by 22%


What makes backlit displays so bad for sleep?


Visible light is white, but it’s made up of a spectrum of colours.

These indigo, violet, blue, green, yellow, orange and red lights have different effects on melatonin production. Unfortunately, backlit displays emit large amounts of blue light, which is the same as the midday sun and actually makes the body feel more alert.

So seeing the blue lights that are used in smartphones, tablets and laptops at night is like being exposed to a bright sun. It stops melatonin production, which keeps the brain active and delays the onset of sleep.


How to beat blue lights and get a good night’s sleep


The simplest solution to beating blue lights would be to avoid them. But that means no Facebook, Twitter, Netflix or X-box after dusk and avoiding streets lit with LED lamps.

It also means turning off any normal interior lights! Exposure to standard room lights, compared to dimmer lighting, suppresses melatonin in 99% of people.

Of course, going back to candle-lit nights is impractical too. So the answer is to be careful and monitor the use of modern technologies.

  • Blackout blinds, curtains and shutters will help you sleep in complete darkness, blocking out the blue lights of any nearby LED street lamps
  • Use dimmer lights. Lowered light levels have less effect on melatonin production
  • Go for a red LED alarm clock. Red light has less impact on melatonin than blue and won’t cause as many problems should you wake early, check the time and want to fall back to sleep
  • Pick up a book. E-readers and tablets have been found to delay sleep by 10 minutes
  • Stop texting at night. 78% of adults use smartphones before bed, exposing themselves to blue light
  • If you must use an electronic device, make sure it’s on the dimmest setting and hold it at least 12 inches from your eyes. Studies have shown this minimises blue light’s influence on melatonin


Sleep Vs Light Infographic

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