The effect of exposure to artificial light at night (ALAN) on sleep disturbance: a systematic review and meta-analysis

BACKGROUND: Exposure to artificial light at night (ALAN) is an increasingly relevant environmental risk factor that can disrupt circadian rhythms and negatively affects organisms, including humans. OBJECTIVES: This systematic review and meta-analysis of epidemiological observational studies aimed to examine the association between ALAN exposure and sleep disturbance in the general population. METHODS: The protocol was published on PROSPERO (CRD42023433543). A comprehensive search in MEDLINE, Embase, PsycINFO and Web of Science was carried out. Title/abstract screening, full-text screening and risk of bias (RoB) assessment were conducted independently by two reviewers. Data were extracted by one and checked by another reviewer. Effect estimates were pooled using random-effects meta-analyses. A standardized transformation of effect measures into prevalence ratios (PR) was applied using VanderWeele's approach, since sleep-related outcomes are generally not rare. The certainty of evidence was judged using an adapted GRADE approach. RESULTS: A total of 15 studies with 765,838 participants were included in this systematic review. A meta-analysis was conducted with ten studies (691,851 participants). Compared to participants with low or no ALAN exposure, those in the highest exposure group had a 27 % higher risk for sleep disturbance (Pooled PR: 1.27 [1.12; 1.45]). Most studies had a high RoB, mainly due to exposure assessment, but the certainty of the evidence was high. CONCLUSION: This systematic review provides evidence of an association between ALAN exposure and sleep disturbance. However, current research is still limited by methodological challenges. Nevertheless, preventive measures are required, including reducing nighttime lighting and increasing public and policy awareness.