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Outdoor artificial light at night may increase the risk of age-related macular degeneration

Findings from a recent case-control study indicate that exposure to outdoor artificial light at night (OALAN) may increase risk of age-related macular degeneration (AMD).

The team of investigators from the Department of Ophthalmology at Jeju National University College of Medicine in South Korea found that those living in urban areas were more likely to develop incident exudative AMD, with older men ages 70 years or older in these areas at the seemingly highest risk.

The investigators cited sleep disorders, obesity, cardiovascular diseases, cancers, and mental disorders as potential negative health impacts caused by light pollution. The authors note that one of the most widespread yet often overlooked environmental hazards resulting from human activity is light pollution. This is characterized by the disturbance of the nocturnal environment due to light emitted from anthropogenic sources, and its negative effects on human health recently have become a pressing concern. They cited that artificial light at night has been widely acknowledged as having a damaging impact on the retina and optic nerve, including potential direct and indirect damage to ocular tissue.

Data for the study was pulled from the database of the Korean National Health Insurance Service, which insures 99.8% of the South Korean population, from 2008 to 2020. Individuals 50 years and older that were diagnosed with exudative AMD between early 2010 and 2011 were included in the study to consider the typical age of onset. Of the over 126,000 participants, about 4,100 had been diagnosed with AMD.

Participants living in urban areas made up 60% of the study, where the average levels of outdoor artificial light at night were 3 times higher than in urban areas. These regional differences suggest the presence of a potential threshold above which OALAN levels may increase the risk of exudative AMD. The OALAN levels in rural areas may not have surpassed the threshold associated with an increased risk. Additionally, the potential impact of region-specific factors cannot be entirely excluded. The investigators also noted that lifestyle differences between urban and rural areas may have also impacted the study’s findings.

The main source of OALAN data used was the US Air Force Defense Meteorological Satellite Program Operational Linescan System. The data’s saturation is then corrected by the National Geophysical Data Center by merging low, medium, and high fixed-gain image levels and releases global data sets of radiance-calibrated light at night.

To assess OALAN by units of radiance as nanowatts per centimeter squared per steradian, the investigators accessed geocoded addresses through the National Geophysical Data Center’s latest radiance-calibrated light-at-night data. As per the authors, such data have been proposed as a reliable proxy measure for relative levels of nighttime illumination at ground level and have been used recently to assess the effects of light pollution on various co-morbidities.

Investigators excluded over 23,500 participants from the study who experienced depression and sleep disorders to better assess the association between OALAN and the risk of exudative AMD, which was found to be unchanged. Given the many other factors that could be at play, the authors suggest further studies that take a deeper dive into exposure, individual adaptive behaviors, and potential mediators into consideration are recommended.

Source (lightly modified)

To read the academic paper, click here.

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