People with greater exposure to traffic-related air pollution were more likely to have high amounts of amyloid plaques in the brain associated with Alzheimer's disease after death, according to a study published online Oct. 21. February 2024 Neurology®, the medical journal of the American Academy of Neurology. The researchers looked at fine particles, PM2.5which consists of polluting particles less than 2.5 microns in diameter suspended in the air.
The study does not prove that air pollution causes more amyloid plaques in the brain. It only shows an association.
“These results add to evidence that fine particles from traffic-related air pollution affect the amount of amyloid plaque in the brain,” said study author Anke Huels, PhD, of Emory University in Atlanta. . “More research is needed to investigate the mechanisms behind this link.”
For the study, researchers examined brain tissue from 224 people who agreed to donate their brains upon death to advance dementia research. People had died at an average age of 76 years.
The researchers looked at exposure to traffic-related air pollution based on people's home address in the Atlanta area at the time of death. Traffic related PM2.5 The rallies are a major source of environmental pollution in urban areas such as metro Atlanta, where most donors lived. The mean 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 researchers then compared pollution exposure with measures of the signs of Alzheimer's disease in the brain: amyloid plaques and tau tangles. They found that people with greater exposure to air pollution one and three years before they died were more likely to have higher levels of amyloid plaques in the brain. People with 1 µg/m3 Highest PM2.5 Exposure in the year before death was almost twice as likely to have higher levels of plaques, while those with higher exposure in the three years before death were 87% more likely to have higher levels of plaques. plates.
The researchers also looked at whether having the main genetic variant associated with Alzheimer's disease, APOE e4, had any effect on the relationship between air pollution and signs of Alzheimer's disease in the brain. They found that the strongest relationship between air pollution and signs of Alzheimer's was among those who did not have the genetic variant.
“This suggests that environmental factors such as air pollution could be a contributing factor to Alzheimer's in patients in whom the disease cannot be explained by genetics,” Huels said.
One limitation of the study is that the researchers only had people's addresses at the time of their death to measure air pollution, so pollution exposure may have been misclassified. The study also involved primarily highly educated white people, so the results may not be representative of other populations.
The study was supported by the HERCULES Pilot Project, the Goizueta Alzheimer's Disease Research Center, and the Rollins School of Public Health Dean's Pilot and Innovation Grant.