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Review
. 2020 Jun 4;1(1):zpaa002.
doi: 10.1093/sleepadvances/zpaa002. eCollection 2020.

Interventions to reduce short-wavelength ("blue") light exposure at night and their effects on sleep: A systematic review and meta-analysis

Ari Shechter  1   2 , Kristal A Quispe  1 , Jennifer S Mizhquiri Barbecho  1 , Cody Slater  3 , Louise Falzon  4
Affiliations
Review

Interventions to reduce short-wavelength ("blue") light exposure at night and their effects on sleep: A systematic review and meta-analysis

Ari Shechter et al. Sleep Adv. .

Abstract

The sleep-wake and circadian cycles are influenced by light, particularly in the short-wavelength portion of the visible spectrum. Most personal light-emitting electronic devices are enriched in this so-called "blue" light. Exposure to these devices in the evening can disturb sleep. Interventions to reduce short-wavelength light exposure before bedtime may reduce adverse effects on sleep. We conducted a systematic review and meta-analysis to examine the effect of wearing color-tinted lenses (e.g. orange or amber) in frames to filter short-wavelength light exposure to the eye before nocturnal sleep. Outcomes were self-reported or objective measures of nocturnal sleep. Relatively few (k = 12) studies have been done. Study findings were inconsistent, with some showing benefit and others showing no effect of intervention. Meta-analyses yielded a small-to-medium magnitude combined effect size for sleep efficiency (Hedge's g = 0.31; 95% CI: -0.05, 0.66; I2 = 38.16%; k = 7), and a small-to-medium combined effect size for total sleep time (Hedge's g = 0.32; 95% CI: 0.01, 0.63; I2 = 12.07%; k = 6). For self-report measures, meta-analysis yielded a large magnitude combined effects size for Pittsburgh Sleep Quality Index ratings (Hedge's g = -1.25; 95% CI: -2.39, -0.11; I2 = 36.35%; k = 3) and a medium combined effect size for total sleep time (Hedge's g = 0.51; 95% CI: 0.18, 0.84; I2 = 0%; k = 3), Overall, there is some, albeit mixed, evidence that this approach can improve sleep, particularly in individuals with insomnia, bipolar disorder, delayed sleep phase syndrome, or attention-deficit hyperactive disorder. Considering the ubiquitousness of short-wavelength-enriched light sources, future controlled studies to examine the efficacy of this approach to improve sleep are warranted. Systematic review registration: PROSPERO 2018 CRD42018105854.

Keywords: blue light; circadian; intervention; meta-analysis; short wavelength; sleep; systematic review.

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Figures

Figure 1.
Figure 1.
Flow chart for selection of references included in systematic review.
Figure 2.
Figure 2.
Risk of bias of included randomized controlled trials. Plus signs (green circles) indicate low risk of bias. Minus signs (red circles) indicate high risk of bias. Question marks (yellow circles) indicate unclear risk of bias.
Figure 3.
Figure 3.
Risk of bias of included before-after studies. Plus signs (green circles) indicate low risk of bias. Minus signs (red circles) indicate high risk of bias. Question marks (yellow circles) indicate unclear risk of bias.
Figure 4.
Figure 4.
Forest plots of objective sleep outcomes. Comparisons are made between blue blocker lenses condition and control (or to pre-treatment baseline). Effect size, 95% confidence interval (CI), and weight of each study are shown on the right of each panel.
Figure 5.
Figure 5.
Forest plot of self-reported sleep outcomes. Comparisons are made between blue blocker lenses condition and control (or to pre-treatment baseline). Effect size, 95% confidence interval (CI), and weight of each study are shown on the right of the panel.
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