In 2014, Harvard researchers locked twelve adults in a sleep laboratory for two weeks. Each evening they read for four hours before bed — one week on a light-emitting e-reader, the other week a printed book. Same reading time, same bedtime. The only difference was the glow.

The screen week

It took them about 10 minutes longer to fall asleep. They got less REM sleep. Their evening melatonin — the hormone that opens the gates of sleep — was suppressed. And the next morning they were measurably groggier and took longer to feel alert. One variable. Four casualties.

Why your brain falls for it

The blue-enriched light of screens hits the exact photoreceptors that tell your brain whether it's day or night. A novel at 11 PM on a tablet reads, neurologically, as late afternoon. Your brain isn't weak-willed. It's being lied to, politely, in high resolution.

The fix the lab validated: read the paper version. Or at minimum, kill the glow an hour before bed — your melatonin will thank you by morning.

Source

Chang A.-M., Aeschbach D., Duffy J.F., Czeisler C.A. Evening use of light-emitting eReaders negatively affects sleep, circadian timing, and next-morning alertness. Proc Natl Acad Sci USA, 2014 — doi.org/10.1073/pnas.1418490112

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