[ESTABLISHED]Established
Evening light exposure from light-emitting screens measured against melatonin timing and sleep onset
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.
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This library reports what studies found. An entry describes a study's design, its findings in its own terms, and its limits. Nothing here is a claim about what a Sage Co. home does, delivers, or prevents.
Last reviewed August 30, 2026.
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 architecture, 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 this study 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.
evening lightmelatoninsleep onsetrandomized crossover
Elsewhere under Light & Circadian Rhythm
This is the only published entry under this domain.