Air pollution increases macular risk

A new, long-term study has revealed a link between air pollution and an increased risk of age-related macular degeneration.

The study authors say if their findings, which are published online today (25 January 2021) in the British Journal of Ophthalmology, are confirmed, it could open the door to new treatments.

They used data from 115,954 UK Biobank (UKBB) participants aged 40-69 with no eye problems at the start of the study in 2006, to establish if ambient air pollution is associated with a heightened risk of AMD, as it with heart and respiratory diseases.

Participants were asked to report any formal diagnosis of AMD, and using retinal imaging, structural changes in the thickness and/or numbers of light receptors in the retina were assessed in 52,602 people for whom complete data were available in 2009 and 2012.

Measures of ambient air pollution included those for particulate matter (PM2.5), nitrogen dioxide (NO2), and nitrogen oxides (NOx), provided by the Small Area Health Statistics Unit as part of the BioSHaRE-EU Environmental Determinants of Health Project.

Official information on traffic, land use, and topography was also used to calculate the annual average air pollution levels at participants’ home addresses.

Just over 1% – 1286 – of the study participants were diagnosed with AMD and among the 52,602 people whose eyes had been assessed, 75% of those with a clinical diagnosis of AMD had signs of AMD on retinal imaging compared to only 12% of those without a clinical diagnosis of AMD.

After accounting for potentially influential factors, data analysis showed that PM2.5 exposure was associated with an 8% higher risk of AMD, while all other pollutants, except coarse particulate matter, were associated with changes in retinal structure.

Although this was an observational study, the authors say their findings are similar to other research and add to the weight of evidence that ambient air pollution could be associated with AMD through oxidative stress or inflammation.

“Overall, our findings suggest that ambient air pollution, especially fine [particulate matter] or those of combustion-related particles, may affect AMD risk,” they write.

“It is possible that the structural features observed may be unrelated to AMD but associated with pollution-induced retinal toxicity. However, the direction of the relationships between air pollution and both AMD and associated retinal layer thicknesses indicate higher exposure to air pollution may make the cells more vulnerable and increase the risk of AMD.

“Our findings add to the growing evidence of the damaging effects of ambient air pollution, even in the setting of relative low exposure. If [they] are replicated, this would support the view that air pollution is an important modifiable risk factor for AMD.”

Researcher Professor Paul Foster, from University College London, UK, said: “Here 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. Our findings suggest that living in an area with polluted air, particularly fine particulate matter or combustion-related particles that come from road traffic, could contribute to eye disease.

“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.”

Chua SYL, Warwick A, Peto T et al. Association of ambient air pollution with age-related macular degeneration and retinal thickness in UK Biobank. British Journal of Ophthalmology 26 January 2021; doi 10.1136/bjophthalmol-2020-316218


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