Does more outdoor light at night help cause macular degeneration?

As levels of nighttime artificial outdoor light rise, so do the odds for a leading cause of vision loss, age-related macular degeneration (AMD). South Korean researchers found that people living in areas of that country with the highest levels of streetlights and other artificial light had more than double the odds of developing AMD, compared to those living in areas with the lowest levels. That risk remained even after they accounted for confounding factors, factors other than the thing being studied that could be causing the results seen in a study, such as sleep issues and depression, said a team led by Dr. Ahnul Ha, of the department of ophthalmology at Jeju National University College of Medicine. City dwellers may be at particular danger for macular degeneration, since the link between the illness and artificial outdoor light “was found solely in urban areas, where the mean outdoor-artificial-light-at-night level was three times higher than in rural areas,” Ha’s group reported. They published their findings Jan. 16 in JAMA Network Open.

In the study, Ha and her team wondered if the proliferation of artificial light at night could play a role in AMD, since it’s already been linked to conditions such as obesity, heart disease, certain cancers and mental health disorders. There’s also research suggesting that artificial light might harm the retina. Light exposure can damage sensitive retinal cells, Ha’s group noted. It can also upset circadian rhythms and trigger hormonal changes that might also be harmful.

In the new research, Ha and her colleagues analyzed data on over 126,000 South Koreans ages 50 or older. About 4,100 of them had been diagnosed with AMD. People’s residences were divided into four groups, ranked by how much artificial outdoor light they might be exposed to at night.  The researchers discovered that older people who lived in urban areas with the highest levels of outdoor artificial light had 2.17 times the odds of developing AMD, versus folks living in areas with the lowest levels. Living in an area that had even just a bit more nighttime artificial light (compared to areas with the lowest levels) was still linked to a 12% higher risk for AMD. That suggests that as levels of artificial light rise, so do the odds for the eye disease.  After adjustment for possible sleeplessness or depression the findings were unchanged. The risk rose with age, and men seemed to be more affected than women, the study found. Other factors—obesity, smoking and drinking—also seemed to strengthen the link between outdoor light at night and AMD.

Dr. Matthew Gorski, an ophthalmologist at Northwell Health in New Hyde Park, N.Y. who was not involved in the study, stressed that the study “does not show any causality. It doesn’t show or prove that outdoor light causes macular degeneration.” “I think this is just a first datapoint and additional studies are going to be needed to confirm whether these results are in fact true,” he added.

Edited by D. Wilcox BSN RN and M. Kaplan, PhD. 

Sources: 

Ernie Mundell, Medical Xpress, January 17, 2024; see source article  John Gever, MedPage Today, January 16, 2024; see source article