High levels of exhaust pollutants may raise risk for degenerative eye disease

Exposure to high levels of exhaust may raise the risk of the vision-robbing disease called age-related macular degeneration (AMD), a new study suggests.

In a study of nearly 40,000 people in Taiwan, researchers found that high levels of exhaust could nearly double the risk of the age-related eye condition, which damages the macula, the part of the eye needed for sharp, central vision. People with AMD have trouble seeing straight ahead.

Only people with the highest exposure to exhaust had an increased risk of age-related macular degeneration (AMD), meaning that “if we can reduce exposure and try not to be in the highest exposure group, the risk can be significantly reduced,” said study co-author Dr. Suh-Hang Hank Juo, a distinguished professor at the China Medical University in Taiwan.

“Therefore, do not go jogging on the road side when there are lots of cars and try not to go outside during the heavy traffic hours,” Juo said in an email.

To investigate whether vehicle pollution, which has previously been tied to increased risks for respiratory and cardiovascular diseases, also impacts the risk for AMD, Juo and his colleagues turned to two large data sets: The Longitudinal Health Insurance Database (LHID) and the Taiwan Air Quality Monitoring Database (TAQMD).

From the insurance database, the researchers selected patients who were aged 50 or older when they were enrolled, who did not have signs of AMD at that point, and who lived in areas where there were air-quality monitoring stations.

As reported in the Journal of Investigative Medicine, the researchers divided the patients into four groups depending on the level of pollutant exposure. Of the 39,819 patients in the study, 1,442 developed AMD during 11 years of follow-up. After accounting for other factors that might influence the risk of AMD, such as age, gender, household income and underlying illnesses, the researchers determined that people living in areas with the highest levels of vehicle-generated pollution were 84% more likely to develop AMD compared to those exposed to the lowest levels.

The new research is interesting but “it is a longitudinal observational study and can only show an association but not prove a cause-effect relationship,” said Dr. Fernando Arevalo, a professor of ophthalmology at the Johns Hopkins University School of Medicine and chairman of ophthalmology at the Johns Hopkins Bayview Medical Center, both in Baltimore, Maryland. “AMD is multifactorial and many genetic, as well as environmental factors, play a role in its development and that may confound the results. Further studies are needed.”

While the study doesn’t prove pollution causes AMD, “it’s very, very intriguing,” said Dr. Avnish Deobhakta, an assistant professor of ophthalmology at the Icahn School of Medicine and the Eye and Ear Infirmary at Mount Sinai in New York.

Scientists already know that smoking increases the risk of AMD, Deobhakta said, adding that “smoking is the highest controllable risk factor.” Inhaled pollutants may work in a similar way, he added.

Dr. Joseph Martel, an assistant professor of ophthalmology at the University of Pittsburgh, suspects that, as with smoking, air pollution may lead to oxidative damage, which “in the eye is known to be associated with macular degeneration.”

That’s why doctors often prescribe an antioxidant concoction of vitamins and minerals to help slow AMD, Martel said. It’s also suggested that people with AMD consume lots of green, leafy vegetables, like spinach, he added.