In a new study, researchers found that long-term exposure to pollutants from vehicle exhaust is linked to a heightened risk of the common eye condition age-related macular degeneration, or AMD.
Exposure to the highest levels of air pollutants was associated with an almost doubling in risk among people aged 50 and older.
AMD is a neurodegenerative condition that affects the middle part of the retina, known as the macula.
It is one of the most common causes of poor vision in older people and is most likely caused by an interplay between genetic and environmental risk factors.
Long-term exposure to air pollution has been linked to a heightened risk of several conditions, including respiratory and heart diseases.
But less is known about its potential effects on eye health.
In the study, the researchers analyzed national health insurance and air quality data from 1998 to 2010 to see if there might be a link between exposure to the pollutants nitrogen dioxide (NO2) and carbon monoxide (CO) and a heightened risk of AMD.
As the condition is more common among older age groups, the researchers focused only on 39,819 people aged 50 and above, most of whom lived in either highly (30%) or moderately (32.5%) urbanized areas.
Because there are seasonal variations in air pollutant levels, the researchers calculated an average annual exposure, which was categorized into four different levels.
During the monitoring period, 1442 people developed AMD.
The team found those with the highest level of exposure to NO2 (more than 9825.5 ppb) were nearly twice (91%) as likely to develop AMD as those exposed to the lowest level (less than 6563.2 ppb).
And people who were exposed to the highest level of CO (more than 297.1 ppm) were 84% more likely to develop AMD than those exposed to the lowest level (less than 195.7 ppm).
The highest rate (5.8%) of newly diagnosed AMD was among people living in the area with the highest level of CO exposure.
The team says this is an observational study, and as such, can’t establish a cause.
In addition, the data didn’t include information on other risk factors, such as smoking, genetics, and inflammation.
This is the first study of its kind to demonstrate a strong link between AMD and high levels of ambient NO2 and CO.
Previous research has implicated NO2 in heart and neurological diseases, and as the retina is part of the central nervous system, there is a plausible biological explanation for its vulnerability to this pollutant.
The lead author of the study is Kuang-Hsi Chang from Tungs’ Taichung Metroharbor Hospital, Taichung, Taiwan.
The study is published in the Journal of Investigative Medicine.
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