Evening light exposure from light-emitting screens measured against melatonin timing and sleep onset
Chang AM, Aeschbach D, Duffy JF, Czeisler CA (2015) · Proceedings of the National Academy of Sciences 112(4):1232–1237
In an inpatient crossover trial, reading from a light-emitting device before bed was reported to delay melatonin onset and lengthen time to fall asleep relative to reading a printed book.
What they studied
A randomized, crossover inpatient study conducted in a controlled research setting over two weeks.
Twelve healthy adults read from a light-emitting device for four hours before bed on five consecutive evenings, and from a printed book under dim light on five other evenings.
Melatonin timing, subjective sleepiness, sleep-onset latency, sleep-stage structure, and next-morning alertness were measured.
What they found
The authors reported that evenings with the light-emitting device were followed by later melatonin onset compared with the printed-book condition.
Participants were reported to take longer to fall asleep, to report less evening sleepiness, and to show reduced next-morning alertness in the device condition.
The effects reported are for a specific evening light exposure in a controlled inpatient setting.
What it does not establish
Twelve healthy adults in a research facility; not a home setting and not a general population.
The exposure studied is a hand-held screen at close range, not ambient room lighting.
The study measures circadian and sleep timing, not long-term health outcomes.
This entry reports the study. It is not a statement about any building Sage Co. designs or constructs.
Source
- Chang AM, Aeschbach D, Duffy JF, Czeisler CA (2015). Evening use of light-emitting eReaders negatively affects sleep, circadian timing, and next-morning alertness · Proceedings of the National Academy of Sciences 112(4):1232–1237 · Read at the source
Last reviewed August 30, 2026.
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