A new study conducted by a team of scientists from Emory University in the USA covers data from over 27 million people aged 65 and older from 2000 to 2018, among whom about three million developed Alzheimer's disease.
The researchers also examined the prevalence of three common comorbid conditions—stroke, hypertension, and depression—to determine how they might influence the risk of developing Alzheimer's disease.
For the analysis, data on air pollution from fine particulate matter (PM₂.₅) to which participants were exposed based on their place of residence was used.
Fine particles pose a danger as they can penetrate deep into lung tissue and enter the bloodstream. Major sources of pollution include vehicle exhaust, emissions from power plants and industrial facilities, wildfires, as well as household burning of wood and fossil fuels.
The study found that polluted air directly affects the brain, not through the mediation of other chronic diseases. It was established that the link between air pollution and Alzheimer's disease is particularly pronounced in individuals who have suffered a stroke.
The authors of the study emphasized that the data show that individuals who have had a stroke may be more vulnerable to the negative effects of air pollution on brain health, indicating an important intersection of environmental and vascular risk factors.
Long-term exposure to fine particulate matter is also associated with an increased risk of developing chronic diseases, including cardiovascular disorders and mental illnesses.
However, the study has limitations. The level of pollution was assessed based on postal codes rather than specific addresses, and only outdoor air was considered, without accounting for indoor pollution arising from cooking, heating, etc.
Researcher Mark Dallas from the University of Reading, who was not involved in this study, noted that despite significant limitations, the results are consistent with existing data that air pollution is a modifiable risk factor for dementia. He added that this confirms the simple truth: the quality of the air people breathe over many years affects the health of their brains over time.
