Woman sleep on bed

The Night, and Sleep, Need Darkness

We are losing the night.  Most parts of the world are lit up with streetlights and other sources of brightness so that — seen from space — the earth looks like a round Christmas tree. Pretty, but dangerous at many levels. Light at night is for all living organisms, from trees to moths to humans, bad news. Biological clocks get confused, reproduction is prevented, metabolism altered, and in humans, sleep is disturbed.  The night needs darkness.

In humans in the evening, a physiological cascade begins with melatonin secretion, which leads to warm feet and hands, which in turn cause sleepiness and quick falling asleep.   Light blocks melatonin synthesis — and, as a result, blocks falling asleep easily.  This leads to the following darkness hints to get ready for sleep:

Avoid light in the evening

  • A couple of hours before bedtime, make sure you are in a soft warm light atmosphere and not exposed to bright light either outdoors or in a room with cool white lamps. As we now have learned, blue-green wavelengths stimulate alertness, which is not what we want at this time of night.
  • If you are outdoors or in a bright environment at night, consider wearing amber-colored blue-blocking eyeglasses. By preventing continued alertness, they help prepare you for sleep. Importantly, they’re fine for vision.
  • Think about installing an amber light (which blocks the blue wavelengths) in the bathroom (with an evening switch from the usual white light). You might not look so good in the mirror while brushing teeth, but you will get sleepy more quickly. Such a night light might also be good in the bedroom, if required.
  • This might be a good idea particularly for the elderly, who often have broken sleep during the night and get up to go to the bathroom more than once. If the bathroom (and bedroom) night lights are amber, it’s enough light to see by and to avoid falls. Unlike the white light of normal lamps which make it hard to go back to sleep, amber lights allow you to return to sleep very quickly.
  • In the evening, avoid computer or laptop screens, cell phone or iPad (easier said than done!), which all have a blue-ish background unless replaced by the manufacturers with a screen turning amber at twilight. You can install your own amber evening light program with the popular app, f.lux.
  • For children and adolescents, a limitation of nighttime cell phone or iPad use is doubly important. Children have transparent lenses and wider pupil size than adults, leaving them more vulnerable to evening light, which then keeps them awake. Teenagers have a biological clock that drifts later and later each year. Exposure to light at night is even worse for teens, since they can no longer get to sleep at a reasonable hour. One solution in the kids’ bedroom is the amber night light.
  • Outside light from street lamps. If your bedroom is facing a street, make sure street lamp light is blocked by thick curtains. You don’t want a continuously lit environment when you’ve turned out the lights.

For more hints on how to fall asleep quickly, see The Secrets of Falling Asleep.