In a large observational study published in the British Journal of Ophthalmology, researchers have found a link between air pollution and an increased risk of developing age-related macular degeneration (AMD), a progressive condition that leads to severe visual impairments that could become irreversible.
There are known risk factors that contribute to the development of AMD such as old age, high blood pressure, and being overweight, as well as a genetically inheritable component that runs in families, however, the exact cause of AMD has not yet been fully explained. Much work has gone into understanding the genetic origins of AMD and whether stem cell and gene therapies might be able to reverse or prevent the process, but more needs to be done to understand the factors that put individuals at higher risk for developing the condition.
Now air pollution, already a grave health concern in big cities around the world, has been linked to an 8 percent increased risk of developing AMD.
“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," said lead author Professor Paul Foster from University College London in a press release. "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."
The authors of the cross-sectional study looked at data from 115,954 participants from the UK Biobank (UKBB) that were between the ages of 40 and 69 years old and had no visual impairments at the start of the study back in 2006.
Over time, the participants had to self-report any formal diagnosis of AMD by a doctor. Using retinal imaging (non-invasive optical coherence tomography), the researchers assessed any structural changes (amount of light receptors and the thickness) of the retina, the part of the eye involved in AMD progression, in 52,602 people from the original total group that had complete data sets available in 2009 and 2012.
Furthermore, using data collected from the Small Area Health Statistics Unit, part of the BioSHaRE-EU Environmental Determinants of Health Project, the researchers calculated the average annual air pollution at the participants' home addresses. Two key pollutants were looked at, nitrogen dioxide (NO2), and nitrogen oxides (NOx), referred to as fine particulate matter (PM2.5).
Out of the total number of study participants, 1,286 were diagnosed with AMD over time. Out of the 52,602 participants who had undergone the eye assessment during the study period, 75 percent that had a clinical diagnosis of AMD also had structural changes in the eye associated with AMD picked up by retinal imaging exams by the end of the study. Out of the participants that did not have a clinical diagnosis of AMD, 12 percent had structural changes associated with the condition.
Accounting for additional risk factors, such as lifestyle and comorbid conditions, the researchers found that the participants that had the highest fine particulate matter (PM2.5) at their home address had an 8 percent higher risk of AMD.
"Higher exposure to air pollution was also associated with structural features of AMD. This may indicate that higher levels of air pollution may cause the cells to be more vulnerable to adverse changes and increase the risk of AMD.” said Dr Sharon Chua, first author of the study.
The researchers note this was an observational study, which doesn't seek a cause, and although their new findings are in line with other findings from around the world, more work needs to be done to understand the potential link between air pollution and AMD.
"Further studies examining both outdoor and indoor ambient air pollution estimates on AMD and outer retinal structures may help to substantiate our findings and understand the implications for retinal disease associated with aging. If our findings are replicated, this would support the view that air pollution is an important modifiable risk factor for AMD," they concluded.