More Nighttime Outdoor Artificial Light May Increase Wet AMD Risk

Ahnul Ha, MD

Credit: ResearchGate

A new study suggested higher levels of residential outdoor artificial light at nighttime were associated with an increased risk of incident wet age-related macular degeneration (AMD), which remained after adjustment for individual- and area-level risk factors.¹

The population-based case-control study using nationwide population-based data in South Korea identified all individuals aged ≥50 years with newly diagnosed wet AMD between January 2010 and December 2011. Data revealed the association between higher levels of light exposure and wet AMD followed a nonlinear pattern, with a slope that became more pronounced at higher outdoor artificial light exposure levels (​​approximately 110 nW/cm²/sr).

“These findings align with the increasing body of evidence that emphasizes the negative impact of outdoor artificial light at night on health, further implicating outdoor artificial light at night as a potential risk factor for wet AMD,” wrote the investigative team, led by Ahnul Ha, MD, from the department of ophthalmology at Jeju National University College of Medicine.

Environmental factors linked to AMD risk have become the center of growing research interest, with light pollution being one of the most widespread and overlooked environmental hazards.² These potential detrimental health effects may result from circadian rhythm disruptions and subsequently impaired hormone secretion, including those linked to sleep disturbances. Artificial light at night has shown a notable impact on both the retina and the optic nerve, leading to damage to ocular tissue.

Across the case-control study, Ha and colleagues assessed the association between residential outdoor artificial light at night and the risk of wet AMD.¹ The incorporation of patients in the Korean National Health Insurance Service database diagnosed in 2010 and 2011 allowed for a ≥10-year follow-up period. Investigators also incorporated 1:30 birth-year and sex-matched controls who had not been diagnosed with wet AMD until 2020.

Sources of outdoor artificial light at night data from the US Air Force Defense Meteorological Satellite Program Operational Linescan System were obtained by the investigative team. An objective measure of mean outdoor artificial light at night was expressed for each geocoded address during 2008 and 2008 for a composite view of persistent nighttime illumination. A total of 4078 patients with newly diagnosed wet AMD and 122,340 wet AMD-free controls (126,418 participants; mean age, 66.0 years; 78,244 men [61.9%]) were included in the analysis.

The analysis showed higher outdoor artificial light at night at an individual’s residence was associated with a greater risk of incident wet AMD. In the fully adjusted model, the hazard ratio (HR) in the highest quartile was 2.17 (95% CI, 1.89 - 2.49) for incident wet AMD. Moreover, the analysis showed an IQR (55.8 nW/cm2/sr) increase in outdoor artificial light at night level was associated with a hazard ratio of 1.67 (95% CI, 1.56 - 1.78) for incident wet AMD.

Subgroup analyses revealed an IQR increase in outdoor artificial light at night was associated with a greater risk of incident wet AMD among those living in urban areas (HR, 1.46; 95% CI, 1.33 - 1.61), but there was no association for those living in rural areas (HR, 1.01; 95% CI, 0.84 - 1.22). Data showed the mean outdoor artificial light at night levels were 3 times higher (61.2 nW/cm²/sr) in urban areas, compared with rural areas (20.6 nW/cm²/sr).

Ha and colleagues indicated the observed regional differences may indicate a potential threshold above which outdoor artificial light at night levels influence the risk of wet AMD. They noted the levels in rural areas may not have exceeded this identified risk threshold, but the impact of region-specific variables should be considered.

“Despite our consideration of potential confounding factors, there remains a possibility that unaccounted variables, such as diet or lifestyle patterns, could have influenced the results in the differences between rural and urban areas,” investigators wrote.

References

1. _{Kim SH, Kim YK, Shin YI, et al. Nighttime Outdoor Artificial Light and Risk of Age-Related Macular Degeneration. JAMA Netw Open. 2024;7(1):e2351650. doi:10.1001/jamanetworkopen.2023.51650}
2. _{Cao M, Xu T, Yin D. Understanding light pollution: recent advances on its health threats and regulations. J Environ Sci (China). 2023;127:589-602. doi:10.1016/j.jes.2022.06.020PubMed}