Impact of artificial light at night on obesity and overweight: a systematic review and meta-analysis.

BACKGROUND

Global obesity rates are rising sharply, prompting interest in environmental drivers beyond diet and activity. Widespread artificial light at night disrupts circadian rhythms and metabolism. potentially elevating obesity risk, but evidence syntheses are outdated and limited.

METHODS

We conducted a systematic search of databases including PubMed, EMbase, Cochrane Library, and Web of Science. Eligible observational studies (cohort or cross-sectional) were required to report adjusted risk estimates (odds ratio [OR], relative risk [RR], or hazard ratio [HR] with 95% confidence intervals [95% CI]) for obesity or overweight, with quantifiable LAN exposure. Study quality was evaluated using the Newcastle-Ottawa Scale (NOS) for cohort studies and the AHRQ criteria for cross-sectional studies. A random-effects model was applied for effect size pooling, alongside subgroup analyses stratified by geographic region, age, and sex, supported by sensitivity analyses and Egger's test for publication bias assessment.

RESULTS

Our analysis included 13 studies involving 867,647 participants (9 cross-sectional and 4 cohort studies). A significant 14% increased risk of obesity was observed in the highest LAN exposure group compared to the lowest (OR = 1.14, 95% CI: 1.07-1.22; I² = 92.5%, P < 0.001). For overweight risk, a 7% increase was noted (OR = 1.07, 95% CI: 1.00-1.15; I² = 92.5%, P < 0.001). Regionally, the strongest association was in North America (OR = 1.21, 95% CI: 1.10-1.32; I² = 46.6%, P = 0.132) and significant in Asia (OR = 1.14, 95% CI: 1.06-1.21; I² = 85.5%, P < 0.001), but not in Europe. Age-wise, both adults (OR = 1.16) and adolescents (OR = 1.17) exhibited significant associations (P < 0.05), with no notable differences between sexes. All studies were deemed high quality (mean NOS score: 7.50; mean AHRQ score: 7.56), and sensitivity analyses confirmed the findings with no evidence of publication bias (P > 0.05).

CONCLUSIONS

Exposure to LAN significantly correlates with increased obesity and overweight risks, influenced by geographic and age-specific factors. These results highlight LAN as a noteworthy environmental risk factor for metabolic health, advocating for informed public health strategies, including region-specific lighting regulations and "screen curfews" for adolescents.