Air pollution from traffic appears to be linked to some of the more severe forms of dementia, potentially serving as a significant cause among individuals not genetically predisposed to the condition, according to new research.
Conducted in Atlanta, Georgia, the study discovered a correlation between higher exposure to traffic-related fine particulate matter air pollution and increased levels of amyloid plaques in the brains of subjects, a hallmark of Alzheimer’s disease.
The findings raise concerns, especially for urban dwellers and those residing near busy roads, highlighting additional health risks posed by road traffic pollution beyond its known impacts on climate change and respiratory diseases.
Researchers from Emory University in Atlanta focused their investigation on the effects of PM2.5, a type of fine particulate matter less than 2.5 microns in diameter, known to penetrate deeply into living tissues including the brain by crossing the blood-brain barrier.
PM2.5 concentrations, largely stemming from traffic, constitute a major component of ambient pollution in metro-Atlanta and urban areas globally.
The study analyzed brain tissue from 224 deceased individuals in Atlanta, 90% of whom had been diagnosed with some form of dementia and had consented to brain donation for research purposes.
The researchers also assessed the levels of traffic-related PM2.5 pollution at the subjects’ residences during the years leading up to their deaths.
They found that average PM2.5 exposure levels in the year before death were 1.32 micrograms per cubic meter (µg/m3), with a slight increase to 1.35 µg/m3 over the three-year period prior to death.
Lead author Anke Huels, an assistant professor at Emory University, explained the study’s findings:
“We found that donors who lived in areas with higher concentrations of traffic-related air pollution, specifically PM2.5 exposure, exhibited higher levels of Alzheimer’s disease neuropathology in their brains.”
This included an increased presence of amyloid plaques, a key indicator of Alzheimer’s disease severity observed in autopsy samples.
The study revealed a direct association between higher PM2.5 exposure and increased amyloid plaque levels in the subjects’ brains.
Specifically, individuals with a 1 µg/m3 increase in PM2.5 exposure in the year before death were nearly twice as likely to exhibit higher plaque levels, while those with higher exposure over the three years before death were 87% more likely to have high plaque levels.
Huels and her team also investigated whether the presence of the ApoE4 gene variant, a major genetic risk factor for Alzheimer’s disease, influenced the relationship between air pollution and disease severity in the brain.
They found that the impact of air pollution on Alzheimer’s severity was more pronounced among individuals without the ApoE4 allele, suggesting that environmental factors like air pollution may contribute significantly to Alzheimer’s risk in individuals not primarily at genetic risk.
These findings underscore the potential role of air pollution in exacerbating Alzheimer’s disease pathology, particularly in urban settings where traffic-related PM2.5 levels are a major concern.
