Evening use of light-emitting eReaders negatively affects sleep, circadian timing, and next-morning alertness

Abstract

In the past 50 y, there has been a decline in average sleep duration and quality, with adverse consequences on general health. A representative survey of 1,508 American adults recently revealed that 90% of Americans used some type of electronics at least a few nights per week within 1 h before bedtime. Mounting evidence from countries around the world shows the negative impact of such technology use on sleep. This negative impact on sleep may be due to the short-wavelength-enriched light emitted by these electronic devices, given that artificial-light exposure has been shown experimentally to produce alerting effects, suppress melatonin, and phase-shift the biological clock. A few reports have shown that these devices suppress melatonin levels, but little is known about the effects on circadian phase or the following sleep episode, exposing a substantial gap in our knowledge of how this increasingly popular technology affects sleep. Here we compare the biological effects of reading an electronic book on a light-emitting device (LE-eBook) with reading a printed book in the hours before bedtime. Participants reading an LE-eBook took longer to fall asleep and had reduced evening sleepiness, reduced melatonin secretion, later timing of their circadian clock, and reduced next-morning alertness than when reading a printed book. These results demonstrate that evening exposure to an LE-eBook phase-delays the circadian clock, acutely suppresses melatonin, and has important implications for understanding the impact of such technologies on sleep, performance, health, and safety.

AI evidence extraction

Main findings

Compared with reading a printed book before bedtime, reading on a light-emitting eReader was associated with longer time to fall asleep, reduced evening sleepiness, reduced melatonin secretion, later circadian timing, and reduced next-morning alertness. The abstract concludes that evening exposure to the light-emitting eReader phase-delayed the circadian clock and acutely suppressed melatonin.

Outcomes measured

• sleep onset latency
• evening sleepiness
• melatonin secretion
• circadian timing/phase
• next-morning alertness

Limitations

• Population not specified in the abstract
• Sample size not reported in the abstract
• Exposure details beyond evening use before bedtime are limited in the abstract

{
    "study_type": "other",
    "exposure": {
        "band": "visible light",
        "source": "light-emitting eReader",
        "frequency_mhz": null,
        "sar_wkg": null,
        "duration": "in the hours before bedtime; evening use"
    },
    "population": null,
    "sample_size": null,
    "outcomes": [
        "sleep onset latency",
        "evening sleepiness",
        "melatonin secretion",
        "circadian timing/phase",
        "next-morning alertness"
    ],
    "main_findings": "Compared with reading a printed book before bedtime, reading on a light-emitting eReader was associated with longer time to fall asleep, reduced evening sleepiness, reduced melatonin secretion, later circadian timing, and reduced next-morning alertness. The abstract concludes that evening exposure to the light-emitting eReader phase-delayed the circadian clock and acutely suppressed melatonin.",
    "effect_direction": "harm",
    "limitations": [
        "Population not specified in the abstract",
        "Sample size not reported in the abstract",
        "Exposure details beyond evening use before bedtime are limited in the abstract"
    ],
    "evidence_strength": "low",
    "confidence": 0.9499999999999999555910790149937383830547332763671875,
    "peer_reviewed_likely": "yes",
    "keywords": [
        "eReader",
        "light-emitting device",
        "evening exposure",
        "sleep",
        "circadian timing",
        "melatonin",
        "alertness",
        "printed book",
        "phase delay"
    ],
    "suggested_hubs": []
}

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