Nighttime Outdoor Artificial Light and Risk of Age-Related Macular Degeneration

Abstract

Importance: Light pollution's impact on human health is increasingly recognized, but its link to exudative age-related macular degeneration (EAMD) remains unclear.

Objective: To investigate the association between exposure to outdoor artificial light at night (OALAN) and the risk of incident EAMD.

Design, setting, and participants: In this nationwide population-based case-control study, all individuals 50 years or older with newly diagnosed EAMD between January 1, 2010, and December 31, 2011, were identified with reference to the Korean National Health Insurance Service registration program database for rare and intractable diseases. Birth year- and sex-matched controls (with no EAMD diagnosis until 2020) were selected at a 1:30 ratio. Data were acquired from May 1 to December 31, 2021, and analyzed from June 1 to November 30, 2022.

Exposures: Mean levels of OALAN at participants' residential addresses during 2008 and 2009 were estimated using time-varying satellite data for a composite view of persistent nighttime illumination at an approximate scale of 1 km2.

Main outcomes and measures: The hazard ratios (HRs) and 95% CIs of the association between residential OALAN and risk of incident EAMD were determined based on maximum likelihood estimation after adjusting for sociodemographic characteristics, comorbidities, and area-level risk factors (ie, nighttime traffic noise and particulate matter of aerodynamic diameter ≤10 μm in each participant's administrative district of residence).

Results: A total of 126 418 participants were included in the analysis (mean [SD] age, 66.0 [7.9] years; 78 244 men [61.9%]). Of these, 4078 were patients with newly diagnosed EAMD and 122 340 were EAMD-free matched controls. In fully adjusted models, an IQR (55.8 nW/cm2/sr) increase in OALAN level was associated with an HR of 1.67 (95% CI, 1.56-1.78) for incident EAMD. The exposure-response curve demonstrated a nonlinear, concave upward slope becoming more pronounced at higher levels of light exposure (ie, at approximately 110 nW/cm2/sr). In a subgroup analysis, an IQR increase in OALAN was associated with increased risk of incident EAMD in urban areas (HR, 1.46 [95% CI, 1.33-1.61]) but not in rural areas (HR, 1.01 [95% CI, 0.84-1.22]).

Conclusions and relevance: In this nationwide population-based case-control study, higher levels of residential OALAN were associated with an increased risk of incident EAMD. Future studies with more detailed information on exposure, individual adaptive behaviors, and potential mediators are warranted.

Figure 1.. Map of South Korea Showing 2008-2009 Outdoor Artificial Light at Night

Data are shown in nanowatts per centimeter squared per steradian (nW/cm²/sr). The data were obtained by the Defense Meteorological Satellite Program’s Operational Linescan System. The solid lines delineate the 250 districts of South Korea.

Figure 2.. Association Between Outdoor Artificial Light at Night and Risk of Exudative Age-Related Macular Degeneration (EAMD)

HR indicates hazard ratio. ^aModels included age and sex. ^bModels were additionally adjusted for baseline body mass index; alcohol consumption; exercise status; income level; comorbidities, including hypertension, type 2 diabetes, dyslipidemia, chronic kidney disease, chronic obstructive pulmonary disease, and cancer; fine particulate matter less than or equal to 10 μm in aerodynamic diameter (PM₁₀); and nighttime traffic noise at the residential address. In the comprehensive model, residential area was also incorporated as a covariate. The analyses considered the interaction between residential areas and outdoor artificial light at night. ^cTest for trend is based on the median value for each quartile. ^dAn IQR increase in outdoor light at night at the residential address is 55.8 nW/cm²/sr.

Figure 3.. Exposure-Response Curve for Association Between Outdoor Artificial Light at Night (OALAN) at Residential Address and Risk of Incident Exudative Age-Related Macular Degeneration

We fitted OALAN as a smooth term using a penalized smoothing spline with 4 df. The shaded area represents 95% CIs. HR indicates hazard ratio.