Don't look at a glowing screen in the hour before bed; read a paper book or an e-ink screen instead

Cost

Free. Putting the phone down an hour before bed means working against habit over the long term, which takes willpower.

What you get

In a lab, the same people did both conditions in turn (a crossover trial). One condition was reading an e-book on an iPad before bed at maximum brightness for about 4 hours, 5 nights in a row. The other was reading a paper book in an equally dim room. Reading a glowing e-book before bed made people fall asleep about 10 minutes slower than reading a paper book (25.7 minutes against 15.8 minutes). Evening melatonin was suppressed by 55%. The next day's body clock (circadian rhythm) was delayed by more than 1.5 hours, with melatonin starting to be released at 22:31 against 21:01. The next morning they were sleepier and took longer to wake up fully.

Notes

The number of people was small, and the conditions were tightly controlled in a lab. At everyday phone brightness and usage time, the effect may not be this large. How much a phone's night mode helps was not measured in this study. E-ink screens were not measured either. An e-ink screen with its light off is read, like a paper book, by reflecting room light, so it is grouped with paper books; this is inferred from this study. An e-ink screen with its light on also emits light, and there are no data.

Evidence grade

B : Supported by research but without a precise number, or based on small or single studies.

Sources

1. Chang, Aeschbach, Duffy & Czeisler (2015). Evening use of light-emitting eReaders negatively affects sleep, circadian timing, and next-morning alertness. PNAS. https://doi.org/10.1073/pnas.1418490112

Translated from the Chinese original. Original book, section 3, tip 8. Content may be out of date and rules differ by place. When you actually deal with an agency, a doctor or a court, follow what local officials, doctors and lawyers tell you. Disclaimer