Effects of smartphone use with and without blue light at night in healthy adults: A randomized, double-blind, cross-over, placebo-controlled comparison

2016 · Mixed · Moderate evidence

← Research stream

MixedModerate evidencePaper 1396

Study snapshot

Publicationmanual · 2016

Study typerandomized_trial

Reported directionMixed

Evidence ratingModerate

Abstract

Effects of smartphone use with and without blue light at night in healthy adults: A randomized, double-blind, cross-over, placebo-controlled comparison Jung-Yoon Heo, Kiwon Kim, Maurizio Fava, David Mischoulon, George I. Papakostas, Min-Ji Kim, Dong Jun Kim, Kyung-Ah Judy Chang, Yunhye Oh, Bum-Hee Yu, Hong Jin Jeon. Effects of smartphone use with and without blue light at night in healthy adults: A randomized, double-blind, cross-over, placebo-controlled comparison. Journal of Psychiatric Research. Available online 12 December 2016 Abstract Smartphones deliver light to users through Light Emitting Diode (LED) displays. Blue light is the most potent wavelength for sleep and mood. This study investigated the immediate effects of smartphone blue light LED on humans at night. We investigated changes in serum melatonin levels, cortisol levels, body temperature, and psychiatric measures with a randomized, double-blind, cross-over, placebo-controlled design of two 3-day admissions. Each subject played smartphone games with either conventional LED or suppressed blue light from 7:30 to 10:00PM (150 min). Then, they were readmitted and conducted the same procedure with the other type of smartphone. Serum melatonin levels were measured in 60-min intervals before, during and after use of the smartphones. Serum cortisol levels and body temperature were monitored every 120 min. The Profile of Mood States (POMS), Epworth Sleepiness Scale (ESS), Fatigue Severity Scale (FSS), and auditory and visual Continuous Performance Tests (CPTs) were administered. Among the 22 participants who were each admitted twice, use of blue light smartphones was associated with significantly decreased sleepiness (Cohen's d = 0.49, Z = 43.50, p = 0.04) and confusion-bewilderment (Cohen's d = 0.53, Z = 39.00, p = 0.02), and increased commission error (Cohen's d = −0.59, t = −2.64, p = 0.02). Also, users of blue light smartphones experienced a longer time to reach dim light melatonin onset 50% (2.94 vs. 2.70 h) and had increases in body temperature, serum melatonin levels, and cortisol levels, although these changes were not statistically significant. Use of blue light LED smartphones at night may negatively influence sleep and commission errors, while it may not be enough to lead to significant changes in serum melatonin and cortisol levels. Conclusion In conclusion, this study suggests that nighttime exposure to the blue light LED display of smartphones may negatively affect sleep and commission errors. This was reflected by the suppression of melatonin production, as indicated by the prolonged time to melatonin onset, and the increase in body temperature, although these changes were not great enough to be statistically significant. These findings indicate that sleep and cognitive functions may be more sensitive markers of exposure of blue light from smartphone LED displays than the physiological changes of melatonin, cortisol, and body temperature. sciencedirect.com

Machine Enhanced Logic

AI evidence extraction

Structured fields below were generated from the paper’s abstract and metadata to make the evidence easier to inspect. Automated extraction may be incomplete or incorrect; verify important details against the original paper.

Study typerandomized_trial

Effect directionmixed

PopulationHealthy adults

Sample size22

ExposureSmartphone game use 7:30–10:00 PM (150 min) during two 3-day admissions; conventional LED vs suppressed blue light (cross-over).

Evidence strengthModerateConfidence: 74% · Peer reviewed: yes

Main findings

In 22 participants (cross-over), blue-light smartphone use at night was associated with significantly decreased sleepiness and confusion-bewilderment, and increased commission error. Time to reach dim light melatonin onset 50% was longer with blue light (2.94 vs 2.70 h); body temperature, serum melatonin, and cortisol increased but these changes were not statistically significant.

Outcomes measured

Serum melatonin levels
Dim light melatonin onset (50%) timing
Serum cortisol levels
Body temperature
Mood states (POMS)
Sleepiness (Epworth Sleepiness Scale, ESS)
Fatigue (Fatigue Severity Scale, FSS)
Cognitive performance (auditory and visual CPT; commission error)

Limitations

Small sample size (n=22)
Short-term, immediate effects assessed (two 3-day admissions)
Exposure characterized as blue-light vs suppressed blue light; no EMF/RF exposure metrics reported (e.g., frequency, SAR)

View raw extracted JSON

{
  "study_type": "randomized_trial",
  "exposure": {
    "band": null,
    "source": "smartphone",
    "frequency_mhz": null,
    "sar_wkg": null,
    "duration": "Smartphone game use 7:30–10:00 PM (150 min) during two 3-day admissions; conventional LED vs suppressed blue light (cross-over)."
  },
  "population": "Healthy adults",
  "sample_size": 22,
  "outcomes": [
    "Serum melatonin levels",
    "Dim light melatonin onset (50%) timing",
    "Serum cortisol levels",
    "Body temperature",
    "Mood states (POMS)",
    "Sleepiness (Epworth Sleepiness Scale, ESS)",
    "Fatigue (Fatigue Severity Scale, FSS)",
    "Cognitive performance (auditory and visual CPT; commission error)"
  ],
  "main_findings": "In 22 participants (cross-over), blue-light smartphone use at night was associated with significantly decreased sleepiness and confusion-bewilderment, and increased commission error. Time to reach dim light melatonin onset 50% was longer with blue light (2.94 vs 2.70 h); body temperature, serum melatonin, and cortisol increased but these changes were not statistically significant.",
  "effect_direction": "mixed",
  "limitations": [
    "Small sample size (n=22)",
    "Short-term, immediate effects assessed (two 3-day admissions)",
    "Exposure characterized as blue-light vs suppressed blue light; no EMF/RF exposure metrics reported (e.g., frequency, SAR)"
  ],
  "evidence_strength": "moderate",
  "confidence": 0.74,
  "peer_reviewed_likely": "yes",
  "keywords": [
    "smartphone",
    "blue light",
    "LED display",
    "nighttime exposure",
    "melatonin",
    "cortisol",
    "body temperature",
    "sleepiness",
    "mood",
    "cognitive performance",
    "cross-over",
    "double-blind",
    "placebo-controlled"
  ],
  "suggested_hubs": []
}

AI can be wrong. Always verify against the paper.

AI-extracted fields are generated from the abstract and metadata and may be incomplete or incorrect. This material is for informational purposes and is not medical advice.

Identifiers and source

DOI: Not supplied
PubMed: Not supplied

Read the original paper →

Related papers

← Back to the Research Library