Living in a more polluted area is associated with a greater likelihood of having glaucoma, according to a new University College London (UCL) study (“The Relationship Between Ambient Atmospheric Fine Particulate Matter (PM2.5) and Glaucoma in a Large Community Cohort”) that appears in Investigative Ophthalmology & Visual Science. People in neighborhoods with higher amounts of fine particulate matter pollution were at least 6% more likely to report having glaucoma than those in the least-polluted areas.

“Glaucoma is more common in urban populations than in others. Ninety percent of the world’s population is exposed to air pollution above World Health Organization (WHO) recommended limits. Few studies have examined the association between air pollution and glaucoma.

“Questionnaire data, ophthalmic measures, and ambient residential area air quality data for 111,370 UK Biobank participants were analyzed. Particulate matter with an aerodynamic diameter < 2.5 lm (PM2.5) was selected as the air quality exposure of interest. Eye measures included self-reported glaucoma, intraocular pressure (IOP), and average thickness of macular ganglion cell–inner plexiform layer (GCIPL) across nine Early Treatment Diabetic Retinopathy Study (ETDRS) retinal subfields as obtained from spectral-domain optical coherence tomography. We examined the associations of PM2.5 concentration with self-reported glaucoma, IOP, and GCIPL.

“Participants resident in areas with higher PM2.5 concentration were more likely to report a diagnosis of glaucoma (odds ratio ¼ 1.06, 95% confidence interval [CI] ¼ 1.01–1.12, per interquartile range [IQR] increase P ¼ 0.02). Higher PM2.5 concentration was also associated with thinner GCIPL (b ¼ _0.56 lm, 95% CI ¼ _0.63 to _0.49, per IQR increase, P ¼ 1.2 3 10_53). A dose–response relationship was observed between higher levels of PM2.5 and thinner GCIPL (P < 0.001). There was no clinically relevant relationship between PM2.5 concentration and IOP.

“Greater exposure to PM2.5 is associated with both self-reported glaucoma and adverse structural characteristics of the disease. The absence of an association between PM2.5 and IOP suggests the relationship may occur through a non–pressure-dependent mechanism, possibly neurotoxic and/or vascular effects.”

“We have found yet another reason why air pollution should be addressed as a public health priority, and that avoiding sources of air pollution could be worthwhile for eye health alongside other health concerns,” said the study’s lead author, Paul Foster, PhD, professor of ophthalmic epidemiology & galucoma studies,UCL Institute of Ophthalmology and Moorfields Eye Hospital. “While we cannot confirm yet that the association is causal, we hope to continue our research to determine whether air pollution does indeed cause glaucoma, and to find out if there are any avoidance strategies that could help people reduce their exposure to air pollution to mitigate the health risks. Most risk factors for glaucoma are out of our control, such as older age or genetics. It’s promising that we may have now identified a second risk factor for glaucoma, after eye pressure, that can be modified by lifestyle, treatment, or policy changes.”

The participants’ data was linked to air pollution measures for their home addresses, from the Small Area Health Statistics Unit, with the researchers focusing on fine particulate matter (equal or less than 2.5 micrometers in diameter, or PM2.5).

The research team found that people in the most-polluted 25% of areas were at least 6% more likely to report having glaucoma than those in the least-polluted quartile, and they were also significantly more likely to have a thinner retina, one of the changes typical of glaucoma progression. Eye pressure was not associated with air pollution, which the researchers say suggests that air pollution may affect glaucoma risk through a different mechanism.

“Air pollution may be contributing to glaucoma due to the constriction of blood vessels, which ties into air pollution’s links to an increased risk of heart problems. Another possibility is that particulates may have a direct toxic effect damaging the nervous system and contributing to inflammation,” said the study’s first author, Sharon Chua, PhD, research fellow, at the UCL Institute of Ophthalmology and Moorfields Eye Hospital.

Air pollution has been implicated in elevated risk of pulmonary and cardiovascular disease as well as brain conditions such as Alzheimer’s disease, Parkinson’s disease, and stroke. Particulate matter exposure is one of the strongest predictors of mortality among air pollutants.

This study adds to previous evidence that people in urban areas are 50% more likely to have glaucoma than those in rural areas, suggesting now that air pollution may be a key contributor to that pattern.

“We found a striking correlation between particulate matter exposure and glaucoma. Given that this was in the U.K., which has relatively low particulate matter pollution on the global scale, glaucoma may be even more strongly impacted by air pollution elsewhere in the world. And as we did not include indoor air pollution and workplace exposure in our analysis, the real effect may be even greater,” said Foster.

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