JAMA Network Open · 11 authors, 14 centres
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This population-based case-control study in South Korea found that higher levels of outdoor artificial light at night (OALAN) at the residence were associated with a significantly increased risk of incident exudative age-related macular degeneration (EAMD). The association followed a nonlinear pattern, was strongest in urban areas, and persisted after adjusting for multiple confounders. These findings suggest that light pollution may be a novel, modifiable risk factor for EAMD.
**Background:** Age-related macular degeneration (AMD) is a leading cause of irreversible blindness, and while genetic and traditional risk factors (e.g., smoking, diet) are well-known, environmental factors are increasingly recognized. Artificial light at night (ALAN) is a widespread environmental hazard that can disrupt circadian rhythms and has been linked to various diseases. This study aimed to investigate the association between residential outdoor artificial light at night (OALAN) and the risk of incident exudative AMD (EAMD) using nationwide population-based data from South Korea.
**Methods:** This case-control study used data from the Korean National Health Insurance Service (NHIS) database (2008-2020), which covers 99.8% of the South Korean population. The study included individuals aged 50 years or older who were newly diagnosed with EAMD between 2010 and 2011 (cases) and 1:30 birth year- and sex-matched controls without EAMD until 2020. After exclusions and matching, 4,078 cases and 122,340 controls (total 126,418 participants; mean age 66.0 years; 61.9% men) were analyzed. OALAN exposure was assessed using satellite data from the US Air Force Defense Meteorological Satellite Program Operational Linescan System (DMSP-OLS), providing mean radiance-calibrated light at night (nW/cm²/sr) for each geocoded address for 2008-2009. Cox proportional hazards regression was used to estimate hazard ratios (HRs) for incident EAMD, adjusting for age, sex, body mass index (BMI), smoking, alcohol, physical activity, income, comorbidities (hypertension, diabetes, dyslipidemia, chronic kidney disease, chronic obstructive pulmonary disease, cancer), residential area (urban/rural), nighttime noise, and particulate matter (PM₁₀).
**Key Results:** Higher OALAN was significantly associated with increased risk of incident EAMD. In fully adjusted models, the HR for the highest quartile vs. the lowest was 2.17 (95% CI, 1.89-2.49). Even the second quartile showed a significant risk (HR, 1.12; 95% CI, 1.00-1.25), with a progressive increase across quartiles (P for trend = 0.01). An interquartile range (IQR) increase in OALAN (55.8 nW/cm²/sr) was associated with an HR of 1.67 (95% CI, 1.56-1.78). The exposure-response curve was nonlinear, with a concave upward slope that became more pronounced at higher OALAN levels (approximately 110 nW/cm²/sr). The association was significant only in urban areas (mean OALAN 61.2 nW/cm²/sr; HR per IQR increase 1.46; 95% CI, 1.33-1.61), not in rural areas (mean OALAN 20.6 nW/cm²/sr; HR 1.01; 95% CI, 0.84-1.22). Stratified analyses showed stronger associations in older individuals (≥70 years), men, those with higher BMI (≥25.0), ever smokers, alcohol consumers, urban residents, and those with hypertension or dyslipidemia. Sensitivity analyses excluding participants with depression or sleep disorders did not change the results.
**Clinical Implications:** This study provides evidence that outdoor light pollution is a potential risk factor for exudative AMD, independent of traditional risk factors. The findings are particularly relevant for urban populations, where OALAN levels are higher. The nonlinear relationship suggests a possible threshold effect, with risk increasing markedly above approximately 110 nW/cm²/sr. The results align with experimental data showing light-induced damage to retinal pigment epithelium (RPE) cells and disruption of circadian rhythms. Clinicians should consider light pollution as a potential environmental risk factor when counseling patients about AMD prevention, especially in urban settings. Public health interventions to reduce light pollution, such as shielding streetlights and using warmer-spectrum lighting, may help mitigate AMD risk. Further research is needed to confirm these findings, assess individual-level exposure (including indoor light), and explore the role of light wavelength and adaptive behaviors.