Abstract
Insufficient light exposure is assumed to be related to a wide array of health problems, though few studies focus on the role of whole-day light exposure in the habitual setting in the development of these health problems. The current review aims to describe the association between personal light exposure in the habitual setting and sleep-wake rhythm and mood in healthy adults from the general population.Five databases (Embase, Medline Epub, Web of Science, PsycINFO, and Google Scholar) were searched in June 2019. The inclusion criteria included: assessment directly of light exposure on the participants for at least one full day; reporting on both individual personal light exposure and outcomes. The quality of the papers was assessed using the Quality Assessment Tool for Observational Cohort and Cross-Sectional Studies of the National Heart, Lung and Blood Institute. The current review followed the PRISMA guidelines.In total, 8140 papers were identified in the database search. Twenty-five papers were eventually included in this review. All included studies were cross-sectional, and individual light exposure was usually measured with a wrist-worn device. Five studies received a “good” quality rating, 16 received a “fair” rating, and the remaining 4 a “poor” quality rating. The overall quality of the included studies was considered low because of the lack of intervention studies and the fact that light exposure was measured on the wrist.Given the low quality of the included studies, the current review can only provide a first exploration on the association between light exposure and sleep-wake rhythm and mood in healthy adults from the general population. Limited evidence is presented for a positive relationship between the amount and timing of light exposure on the one hand and rest-activity rhythm and some estimates of sleep architecture on the other. The evidence on an association between light exposure and circadian phase, sleep estimates, sleep quality, and mood is conflicting. Data from intervention studies are needed to gain insight into the causal mechanism of the relationship between light exposure and sleep-wake rhythm and mood.
Highlights
Most of the excluded studies (n = 279) were excluded because they did not report on personal light measurements
Circadian phase of the sleep-wake rhythm seems to be affected by light exposure within the laboratory setting, the implications for the real world are yet to be determined
The current review applied strict inclusion criteria for light exposure measurements and analysis. This way, even though the quality of the included studies was low, this review provides us with more insight into the current evidence on the relationship between personal light exposure, sleep, and mood in the general population
Summary
M.N. Bo€hmer et al / Sleep Health 00 (2021) 1À21. To the external 24h rhythm using external cues called “Zeitgebers,” of which light is the strongest.[1]. Alignment of the circadian rhythm with external day-night rhythm is considered essential for the regulation of the sleep-wake rhythm and mood.[2,3,4] Insufficient, or badly timed, exposure to light can result in desynchronization of the sleep-wake rhythm and sleep problems, which in turn can result in mood problems.[3] Misalignment of circadian rhythms[2,5] and disturbances of the sleepwake rhythm[6] and mood[7] are each associated with poor health outcomes
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