Particulate Air Pollution Correlates with Risk of Alzheimer's Disease
Researchers here use data on air pollution from a single US metropolitan area to show a correlation with Alzheimer's disease risk. Air pollution is shown to increase chronic inflammation via the interaction of particulates with lung tissue, and inflammation is an important component of the onset and progression of neurodegenerative conditions such as Alzheimer's disease. That said, the researchers were primarily interested in traffic as a source of particulate air pollution, and one might think that this introduces a correlation with wealth, given the usual distribution of cost of living versus proximity to major flows of traffic. Wealth and health are a part of a web of correlations including socioeconomic status, life expectancy, education, intelligence, and so forth. It requires some effort to untangle these contributions in human data.
For the study, researchers examined the brain tissue of 224 people who agreed to donate their brains at death to advance research on dementia. The people had died at an average age of 76. Researchers looked at the traffic-related air pollution exposure based on the people's home address in the Atlanta area at the time of death. Traffic-related PM2.5 concentrations are a major source of ambient pollution in urban areas like the metro-Atlanta area where most donors lived. The average level of exposure 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.
Researchers then compared pollution exposures to measures of the signs of Alzheimer's disease in the brain: amyloid plaques and tau tangles. They found that people with higher exposures to air pollution one and three years before death were more likely to have higher levels of amyloid plaques in their brains. 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, while those with higher exposure in the three years before death were 87% more likely to have higher levels of plaques.
Researchers also looked at whether having the main gene variant associated with Alzheimer's disease, APOE e4, had any effect on the relationship between air pollution and signs of Alzheimer's in the brain. They found that the strongest relationship between air pollution and signs of Alzheimer's was among those without the gene variant.