Skip glowing screens for one hour before bed; if you read, use a paper book or an e-ink screen with the front light off
UpdatedGrade BMedium benefitTimeFreeLittle timeHigh willpower
Reading a glowing screen before bed, versus a paper book, delays falling asleep by about 10 minutes. Melatonin is suppressed by 55%. The next day’s body clock shifts more than 1.5 hours later; mornings feel sleepier and take longer to clear.
- Cost
- No money. Putting the phone down for one hour before bed means fighting habit long-term; that takes willpower.
- Benefit
- In the lab the same people did both conditions in turn (crossover). One was reading an e-book on an iPad before bed, brightness at maximum, about 4 hours, for 5 nights in a row. The other was reading a paper book in the same dim room. Reading the glowing e-book delayed sleep onset by about 10 minutes versus paper (25.7 minutes versus 15.8 minutes). Evening melatonin was suppressed by 55%. The next day’s body clock (circadian rhythm) delayed by more than 1.5 hours; melatonin onset was 22:31 versus 21:01. The next morning they were sleepier and took longer to become fully awake.
- Notes
- The sample is small; conditions were tightly controlled in a lab. At everyday phone brightness and use time, the effect may be smaller. How much night mode helps was not measured. E-ink was not measured either. An e-ink screen with the front light off, like paper, is read by reflected room light, so it is grouped with paper; that is an inference from this study. An e-ink screen with the front light on is also emitting light; there is no data.
Sources · 1
- Chang, Aeschbach, Duffy & Czeisler (2015). Evening use of light-emitting eReaders negatively affects sleep, circadian timing, and next-morning alertness. PNAS. doi.org/10.1073/pnas.1418490112