Exhaust pollutants may double AMD risk

Vision robbing disease Age, genes possible risk factors

NEW YORK, Aug 25, (RTRS): 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 coauthor 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

Exposure

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. AfNEW YORK, Aug 25, (RTRS): In people who already have a genetic vulnerability, small-particle air pollution known as black carbon may raise the risk of developing glaucoma, a new study suggests.

Researchers found that in older men with genetic variations that made them especially susceptible to oxidative stress, long-term exposure to black carbon, a pollutant linked to vehicle emissions and other products of combustion, was associated with higher pressures in the eye, according to the study published in JAMA Ophthalmology.

“Oftentimes, when we think about glaucoma we think about risk factors like age and genetic predisposition and we don’t think about the environment,” said the study’s lead author, Jamaji Nwanaji-Enwerem, an MD/PhD candidate at the Harvard Medical School in Boston. “But one thing we’re starting to appreciate more is how the environment impacts health outcomes.”

One area in which there hasn’t been a lot of research is the impact of the environment on eye disease, Nwanaji-Enwerem said.

ter 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

So, he and his colleagues decided to look at the effect of the tiny particles of black carbon, which are smaller than 2.5 microns in diameter and can penetrate deep into the lungs, and from there, into the bloodstream.

The researchers analyzed data from 419 older men from the Boston area who had been participating since the 1960s in a larger US Department of Veterans Affairs aging study. They came in for health exams every three to five years after joining the study and as part of those exams intraocular pressure was measured.

Glaucoma, which can eventually result in blindness if not treated, is most often caused by high intraocular pressure, or high fluid pressure within the eye.

“When eye pressure is too high, it causes damage to the optic nerve, the cable that connects our eyes to the brain and visual pathways,” explained Dr Christopher Starr, an ophthalmologist at New YorkPresbyterian/Weill Cornell Medicine in New York City, who was not involved in the new research. “If you lose cells in that nerve, you lose vision.

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

It usually starts with peripheral vision loss and as time goes on you lose more and more.”

For the study, Nwanaji-Enwerem’s team determined the men’s pollution exposure using a modeling program that included black carbon levels gleaned from 83 monitoring sites and weather data.

The researchers then analyzed the pollution results along with each man’s eye pressure readings and a host of other health and lifestyle factors, including BMI, smoking status, heart disease, blood pressure and diabetes.

Overall, they found no link between pollution and eye pressure. But when they looked just at men who had certain gene versions that made them vulnerable to oxidative stress, the researchers found an association between higher pollution levels and a slight increase in eye pressure.

While interesting, the new study’s findings will need to be duplicated, Starr noted, adding that even if proven, the effects seen in this study are small. “They may not even be clinically significant in the context of glaucoma,” he said.

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 professsor 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.”