Set a screen curfew 60-90 minutes before sleep

All screens off 60-90 minutes before intended sleep time — including television.

Why it works

Melatonin secretion begins approximately 2 hours before habitual sleep time. Blue-spectrum light (480nm wavelength, dominant in LED/LCD screens) suppresses melatonin via ipRGC retinal cells and delays the melatonin onset by up to 90 minutes at typical screen brightnesses. This delays sleep onset and can phase-shift the circadian rhythm over successive nights.

How to do it

1. Set a phone alarm 90 minutes before your target sleep time labelled "all screens off."
2. At the alarm, close the laptop, turn off the TV, and put the phone on charge outside the bedroom.
3. Replace the screen time with low-arousal activity: reading a physical book, stretching, light conversation, bath.
4. After two weeks, track whether sleep onset improves on nights when you comply versus nights when you don’t.

Evidence

Laboratory studies confirm that blue-light exposure in the 60-90 minutes before sleep delays melatonin onset and increases sleep latency. The effect is dose-dependent on light intensity and timing. (rct)

Chang et al. used e-readers at maximum brightness over five nights; effect sizes from casual real-world phone use may be smaller. Blue-light glasses show inconsistent benefits in trials — device removal is more reliable.

Sources

• Chang et al. (2015), evening use of light-emitting eReaders negatively affects sleep, PNAS

Common mistake

Using a blue-light filter app and continuing to scroll until midnight, assuming the filter fully negates the melatonin suppression — it reduces but does not eliminate the effect, and does nothing about conditioned arousal.