A recent study published in JAMA Network Open reveals that higher exposure to artificial outdoor light at night may increase the risk of exudative age-related macular degeneration.
Study: Night-time artificial light exposure linked to increased risk of age-related macular degeneration. Image credit: CGN089 / Shutterstock
Age-related macular degeneration (AMD) is characterized by progressive loss of central vision due to damage to the macular region of the retina. The disease can potentially lead to irreversible blindness. AMD is a multifactorial disease associated with several genetic and non-genetic risk factors.
Advanced age is the most prominent non-genetic risk factor for AMD. Additionally, smoking and low intake of antioxidants are other non-genetic risk factors. In addition to various environmental risk factors, light pollution is known to have significant adverse effects on the retina and optic nerve. High light exposure can damage ocular tissue.
In this study, scientists investigated the impact of nocturnal exposure to artificial outdoor light on the risk of exudative AMD in South Korea. Artificial outdoor light at night refers to changes in natural light levels at night due to artificial light sources. The exudative form of AMD is characterized by the formation of pathological choroidal neovascular membranes beneath the retina, which can cause fluid and blood leakage.
The scientists collected demographic and medical data of adult individuals (aged 50 and above) with newly diagnosed exudative AMD from the database of the Korean National Health Insurance Service’s registration program for rare and intractable diseases between January 2010 and December 2011.
They also identified age- and gender-matched individuals who had not been diagnosed with exudative AMD until 2020 and included them as study controls in the analysis. The scientists obtained medical data of the patients and control subjects from 2010–2011 in 2021 to ensure a follow-up period of at least 10 years.
They used the latest radiation-calibrated nocturnal light data from the National Geophysical Data Center to measure the average intensity of artificial outdoor nocturnal light at the participants‘ residential addresses in 2008 and 2009.
They assessed the association between nocturnal exposure to artificial outdoor light and the risk of exudative AMD after accounting for participants‘ sociodemographic characteristics, comorbidities, and other environmental risk factors such as nocturnal traffic noise and airborne particulate matter.
The study was conducted on a total of 126,418 individuals, including 4,078 patients with exudative AMD and 122,340 control individuals without the disease. Overall, participants with higher nocturnal artificial light exposure outdoors were exposed to higher particulate matter and nocturnal traffic noise. Conversely, participants with lower nocturnal artificial outdoor light exposure had lower levels of physical activity at night.
After adjusting for potential confounders, the analysis revealed that higher nocturnal exposure to artificial outdoor light significantly increased the risk of exudative AMD. An interquartile range (IQR; 55.8 nanowatt/cm2/steradian) increase in nocturnal exposure to artificial outdoor light was associated with a hazard ratio of 1.67 for the occurrence of exudative AMD.
The analysis of the exposure-response curve shape for the association between nocturnal exposure to artificial outdoor light and the risk of exudative AMD showed a nonlinear, concave increase that became more pronounced with higher light exposure.
A subgroup analysis involving 73,551 participants from urban areas revealed that approximately 3.7% of them developed exudative AMD between 2021 and 2011. A similar analysis involving 48,972 participants from rural areas showed that approximately 2.5% of them developed exudative AMD in the same period.
Further analysis showed that an IQR increase in nocturnal exposure to artificial outdoor light was associated with an increased risk of exudative AMD in urban areas, but not in rural areas.
Stratified analysis of the hazard ratio of exudative AMD by personal characteristics at the start of the study revealed that AMD risk was significantly higher due to nocturnal exposure to artificial outdoor light in older individuals, men, smokers, urban residents, and individuals with a higher body mass index. It was also higher in persons with hypertension or dyslipidemia and those with alcohol consumption habits.
This population-based case-control study conducted in South Korea demonstrates that higher nocturnal exposure to artificial outdoor light significantly increases the risk of exudative AMD. Given that AMD is the leading cause of irreversible blindness, future studies are needed to analyze different light exposure levels, individual adaptation behaviors, and potential mediators to better understand the relationship between light exposure and AMD development.