Ambient Air Pollution Tied to Age-Related Macular Degeneration

By Lisa Rapaport

February 01, 2021

(Reuters Health) - People with higher exposure to ambient air pollution are at increased risk for age-related macular degeneration and changes in retinal thickness, a UK study suggests.

Researchers examined data on 115,954 participants in the UK Biobank who were 40 to 69 years old and had no history of eye disease at baseline in 2006. Participants reported any diagnosis of age-related macular degeneration, and a subset of 52,602 people had data from retinal imaging in 2009 and 2012.

A total of 1,286 (1.1%) participants reported developing age-related macular degeneration (AMD) during the study.

Participants with higher levels of exposure to fine particulate matter (PM 2.5) were significantly more likely to develop AMD (odds ratio 1.08). On retinal imaging they also had thinner photoreceptor synaptic region (beta -0.16), thicker photoreceptor inner segment layer (beta 0.04), and thinner retinal pigment epithelium (beta -0.13).

In addition, participants with higher exposure to nitrogen dioxide (NO2) had thicker photoreceptor inner segment layer (beta 0.04) and photoreceptor outer segment (beta 0.17). Those with greater exposure to nitrogen oxide (NOx) had thinner photoreceptor synaptic region (beta -0.10) as well as thicker photoreceptor inner (beta 0.03) and outer 0.05) layers.

"We have identified yet another health risk posed by air pollution, strengthening the evidence that improving the air we breathe should be a key public health priority," said study co-author Paul Foster of the Institute of Ophthalmology at University College London.

"Even relatively low exposure to air pollution appears to impact the risk of AMD, suggesting that air pollution is an important modifiable risk factor affecting risk of eye disease for a very large number of people," Foster said by email.

Among the subset of Biobank participants in the study who had retinal imaging and eye assessments, researchers found that more people with an AMD diagnosis (75%) than those without this diagnosis (12%) showed signs of the condition on imaging.

One limitation of the study is that UK Biobank voluntary participants tend to be healthier than the general population, the study team notes in British Journal of Ophthalmology. Another is that outdoor air pollution exposure was estimated based on participants' home addresses, and they could have had different exposure levels at other locations such as the workplace.

It is also unclear if early- or late-life exposure to air pollution may lead to risk of AMD, or whether cumulative years of exposure across the lifespan might impact the risk, said Dr. Tien Wong, MD, medical director of the Singapore National Eye Center at the National University of Singapore.

"The relationship should be confirmed in a prospective study with clearer measures of definitive AMD over time, before we can understand when air pollution exposure may be harmful," Dr. Wong, who wasn't involved in the study, said by email.

The results are too preliminary to change clinical practice, Dr. Wong said.

"However, clinicians should be aware that these data add to increasing evidence that environmental factors may play a role in AMD," Dr. Wong said.

SOURCE: British Journal of Ophthalmology, online January 25, 2021.