It’s well-known that air pollution has adverse impacts on overall health, contributing to the risk of diseases such as chronic asthma or cardiovascular diseases. Now, a new study shows that higher exposure to air pollution could be linked to high amounts of amyloid plaques in the brains which is associated with Alzheimer's disease.
The study, led by researchers from the American Academy of Neurology (AAN), provided evidence that fine particulate matter from traffic-related air pollution impacts the amount of amyloid plaque—clusters of misfolded protein between nerve cells in the brain. By fine particulate matter, the researchers refer to PM2.5, which consists of pollutant particles of less than 2.5 microns in diameter suspended in air, AAN's press statement explained.
For the study, researchers examined the brain tissue of 224 people who donated their brains at death to improve research on dementia. The people had died at the age of 76. The findings showed that the average exposure level in the year before death was 1.32 micrograms per cubic meter (µg/m3) and 1.35 µg/m3 in the three years before death, the statement elaborated. The findings were published in the journal Neurology.
The researchers found that higher exposures to air pollution one and three years before death were likely to lead to higher levels of amyloid plaques in the brain. Furthermore, people with 1 µg/m3 higher PM2.5 exposure in the year before death were nearly twice as likely to have higher levels of plaques. Meanwhile, those with higher exposure in the three years before death were 87% more likely to have higher levels of plaques, the statement explained.
The findings also showed that the strongest relationship between air pollution and signs of Alzheimer's was among people who did not have APOE e4, the main gene associated with Alzheimer's disease.
"This suggests that environmental factors such as air pollution could be a contributing factor to Alzheimer's in patients in which the disease cannot be explained by genetics," study author Huels said in the statement.
Previous studies have also found an association between air pollution and dementia. For instance, an analysis published in BMJ Journal in April 2023 showed that long exposure to polluted air containing high levels of fine particles has been consistently linked to dementia.
The World Health Organization recommends that average annual PM2.5 levels should be below 5 micrograms. However, most people across the world breathe air that exceeds these limits. The widespread pollution exposure makes the particulate matter a concerning risk factor for dementia.
