Influence of evening light exposure on polysomnographically assessed night-time sleep: A systematic review with meta-analysis

Abstract

Evening exposure to electric light can acutely suppress melatonin levels and adversely affect subsequent sleep. We conducted a systematic review with meta-analysis investigating the influence of evening illuminance levels on polysomnographically (PSG)-assessed sleep. We also explored how melanopsin (expressed in melanopic equivalent daylight illuminance (EDI) affects human sleep features. We included polysomnographic laboratory sleep studies with healthy humans for effects of illuminance and exposure duration, for pre-sleep exposures between 6:00 p.m. to 1:00 a.m. From 440 identified articles, 114 met eligibility criteria for screening, and 21 also reported type of light source/spectral characteristics, with 12 identified as eligible for review. Meta-analysis showed evening light affects sleep latency, sleep efficiency and slow wave sleep, with overall effect sizes (95% confidence interval) of 0.69 (−0.50; 1.88), 0.34 (−0.13; 0.82) and −0.61 (−1.85; 0.62), respectively. Estimated melanopic EDI in the range of 100–1000 lx yielded clear dose–response relationships for sleep latency and sleep efficiency, but not for slow wave sleep. Whilst illuminance and duration indicated no apparent effects for a single evening light exposure on PSG-assessed sleep latency, sleep efficiency and slow wave sleep, we observed evidence for a relationship between light exposure and sleep effects based on melanopic EDI. Hence, melanopic EDI may provide a robust predictor of non-visual responses on human sleep.

Melanopic metrics: Advancing the characterization of everyday light patterns

“…In addition to access to light in the evening providing the capacity to participate in other activities over sleep, and subsequent behavioral delay to bedtime, light in the evening also has an acute alerting effect ( 8 , 9 ) which can further delay sleep onset. This impact is observed by Didikoglu et al in the form of longer sleep onset latency, and confirms prior findings ( 10 – 12 ). In the morning, however, the alerting effects of light support easier waking with more light late in the sleep episode and after waking associated with reduced sleepiness upon waking (also known as sleep inertia), as previously reported in experimental studies ( 13 ).…”

ICNIRP Statement on Short Wavelength Light Exposure from Indoor Artificial Sources and Human Health

“…However, if studies are conducted to compare results of light sources with identical geometry, it is acceptable to measure spectral irradiance (instead of spectral radiance) and then apply the five CIE S026 (CIE 2018) weighting functions. In fact, a recent meta-analysis by Cajochen et al (2022) found that melanopic equivalent daylight illuminance was a robust predictor of evening light exposure effects on sleep.…”

The Ecology of Human Sleep (EcoSleep) Project: Protocol for a longitudinal cohort repeated-measurement-burst study to assess the relationship between sleep determinants and sleep outcomes under real-world conditions across time of year

“…Sleep also changes throughout the year. Since exposure to light not only shapes sleep architecture, entrains circadian rhythms and influences melatonin production [7][8][9][10][11], the change in relative abundance and timing of light over the year (photoperiodical changes) in locations further away from the equator could have an impact on sleep and circadian-related variables. However, evidence on seasonal effects is very mixed and unclear (as summarised by Mattingly et al [12] on sleep duration and timing).…”