A systematic review of the amount and timing of light in association with objective and subjective sleep outcomes in community-dwelling adults

Abstract

Light is considered the dominant environmental cue, or zeitgeber, influencing the sleep-wake cycle. Despite recognizing the importance of light for our well-being, less is known about the specific conditions under which light is optimally associated with better sleep. Therefore, a systematic review was conducted to examine the association between the amount and timing of light exposure in relation to sleep outcomes in healthy, community-dwelling adults. A systematic search was conducted of four databases from database inception to June 2016. In total, 45 studies met the review eligibility criteria with generally high study quality excepting for the specification of eligibility criteria and the justification of sample size. The majority of studies involved experimental manipulation of light (n=32) vs observational designs (n=13). Broad trends emerged suggesting that (1) bright light (>1000 lux) has positive implications for objectively assessed sleep outcomes compared to dim (<100 lux) and moderate light (100-1000 lux) and (2) bright light (>1000 lux) has positive implications for subjectively assessed sleep outcomes compared to moderate light (100-1000 lux). Effects due to the amount of light are moderated by the timing of light exposure such that, for objectively assessed sleep outcomes, brighter morning and evening light exposure are consistent with a shift in the timing of the sleep period to earlier and later in the * Corresponding author. ndautovich@vcu.edu. (N.D. Dautovich).

Lighting in the Home and Health: A Systematic Review

“…Studies using this measurement method were not eligible for inclusion in our systematic review as it lacks consideration for individual level factors, like window covering practices with blinds and location of the bedroom in relation to streetlights, and as such is not always reliable to represent an individual’s exposure to light within the home [ 78 , 79 ]. Nonetheless, there is still further evidence available supporting the negative impact of light at night within the home on health and sleep in particular [ 22 , 76 , 80 , 81 ]. A clear biological explanation for this association exists.…”

Environmental Influences on Sleep in the California Teachers Study Cohort

“…Exposure to bright lights before sleep can delay the release of melatonin, therefore increasing sleep latency and disrupting circadian rhythm ( 4 ). While the direct stimuli of light indoors prior to sleep has been shown to delay sleep onset and reduce sleep quality ( 5 ), so has artificial light at night (ALAN) from the outdoor environment ( 6 , 7 ). ALAN has been increasing several percent yearly over the past decades due to increasing human development and urbanization and may be playing a role in disrupting circadian rhythm ( 8 , 9 ).…”

Light up: an intervention study of the effect of environmental dynamic lighting on sleep–wake rhythm, mood and behaviour in older adults with intellectual disabilities

“…2015; Dautovich et al . 2019), lower sleep quality (Aarts et al . 2018) and mood complaints (Espiritu et al .…”

“…Light enters the eye, which acts on the intrinsically photosensitive retinal ganglion cells (ipRGC), which project to the suprachiasmatic nucleus through the retinohypothalamic tract (Hattar et al 2002). In the general population, insufficient or badly timed light exposure is related to disrupted sleep (Linton et al 2015;Dautovich et al 2019), lower sleep quality (Aarts et al 2018) and mood complaints (Espiritu et al 1994;Driesen et al 2010;Moreno et al 2019;Burns et al 2021).…”