International. Air pollution is linked to an increased risk of progressive and irreversible vision loss, known as age-related macular degeneration (AMD), reveals a long-term study led by researchers at UCL (University College London).
They found that people in the most polluted areas were at least 8% more likely to report having AMD, according to findings published in the British Journal of Ophthalmology.
Lead author Professor Paul Foster (UCL Institute of Ophthalmology) said: "Here we have identified another health risk posed by air pollution, reinforcing the evidence that improving the air we breathe should be a key public health priority. Our findings suggest that living in an area with polluted air, particularly fine particles or combustion-related particles that come from road traffic, could contribute to eye diseases.
"Even relatively low exposure to air pollution appears to affect amd risk, suggesting that air pollution is an important modifiable risk factor that affects the risk of eye disease for large numbers of people."
AMD is the leading cause of irreversible blindness among people over the age of 50 in high-income countries, and the number of people affected is projected to reach 300 million by 2040. Known risk factors include old age, smoking, and genetic structure.
Air pollution has been linked to brain conditions such as Alzheimer's disease, Parkinson's disease and strokes, while a 2019 study by the same research team found that air pollution was linked to an elevated risk of glaucoma. Exposure to particulate matter is one of the strongest predictors of mortality among air pollutants.
To see if air pollution might also be involved in AMD risk, the researchers relied on data from 115,954 UK Biobank study participants aged between 40 and 69 with no eye problems at the start of this study in 2006.
Participants were asked to report on any formal diagnosis of AMD made by a physician. And structural changes in thickness and/or number of light receptors in the retina, indicative of AMD, were evaluated in 52,602 of the participants, for whom complete data were available in 2009 and 2012, using retinal imaging (non-invasive optics coherence tomography or OCT).
Environmental air pollution measures included those of particulate matter (PM2.5), nitrogen dioxide (NO2) and nitrogen oxides (NOx). Estimates for these were provided by the Small Area Health Statistics Unit as part of the BioSHaRE-EU Environmental Determinants of Health Project. Official information on traffic, land use and topography was used to calculate the average annual air pollution levels in the addresses of the participants' homes.
The research team found that people in areas with higher levels of fine particulate matter pollution were more likely to report having AMD (specifically, they found an 8% difference in AMD risk between people living in the 25th and 75th percentiles of pollution levels), after accounting for potentially influential factors such as underlying health conditions and lifestyle. All pollutants, except coarse particles, were associated with changes in the structure of the retina.
The researchers caution that this observational study cannot confirm the cause, but their findings align with evidence from other parts of the world.
While they cannot yet confirm a mechanism, they suggest that ambient air pollution could be plausibly associated with AMD through oxidative stress or inflammation.
Dr Sharon Chua (UCL Institute of Ophthalmology), the first author of the paper, adds: "Increased exposure to air pollution was also associated with the structural characteristics of AMD. This may indicate that higher levels of air pollution can make cells more vulnerable to adverse changes and increase the risk of AMD."
The study was funded by Moorfields Eye Charity, the NIHR Biomedical Research Centre at Moorfields Eye Hospital NHS Foundation Trust and the UCL Institute of Ophthalmology, Alcon Research Institute and the International Glaucoma Association.
Source: Sciencedaily
