Sleep and light: bright days, dim evenings

What the sources say

• NHLBI: spend time outside each day when possible; avoid "bright artificial light, such as from a TV or computer screen" in the hour before bed; a low-level night light is fine if you need one; keep your bedroom "quiet, cool, and dark".
• NHS: make sure your bedroom is dark and quiet, using curtains, blinds, an eye mask or ear plugs if needed.

One study

In a laboratory study published in PNAS in 2015, people who read on a light-emitting e-reader before bed took longer to fall asleep, had reduced evening sleepiness and melatonin secretion, a later circadian clock and lower next-morning alertness than when they read a printed book. It is one study of one setup, so treat it as supporting the official advice rather than proof for every device.

Tonight

• Get outside in daylight when you can.
• In the last hour, switch to lamps and put bright screens away; read on paper if you like.
• Check your bedroom: curtains, blinds, or an eye mask if streetlight comes in.

The SleepNoise player uses a dark theme, so it does not light up the room.

Try it for 7 nights

Choose one light change, such as screens away 60 minutes before bed, and tick each night you do it. Combine it with the wind-down routine and the Bedtime Challenge.

Saved on this device only. Works offline. Clear

Sources

• NHLBI (US National Institutes of Health): Healthy sleep habits
  Page updated 24 March 2022; checked 2026-10-19
• NHS: Insomnia
  Page reviewed 19 March 2024; checked 2026-10-19
• Chang AM, Aeschbach D, Duffy JF, Czeisler CA. Evening use of light-emitting eReaders negatively affects sleep, circadian timing, and next-morning alertness. PNAS 2015;112(4):1232-1237
  Peer-reviewed abstract, published 27 Jan 2015; record verified 2026-10-19

Questions

Related: Wind-down routine (20 minutes) · A 9pm bedtime