7.2 million Americans suffer from this incurable disease.
A new study in the U.S. has revealed a direct link between air pollution and the development of Alzheimer's disease. Researchers from Emory University (Georgia) found that fine particles PM2.5 can increase the risk of Alzheimer's disease directly, rather than indirectly through cardiovascular or pulmonary diseases, as previously thought. The study was published in the journal PLOS Medicine.
The researchers examined data from more than 27 million Medicare recipients aged 65 and older from 2000 to 2018. They then compared information about Alzheimer's patients with air pollution levels in their residential areas. Concurrently, the researchers assessed data on three comorbid conditions (hypertension, stroke, and depression) to determine how they influence the development of Alzheimer's.
The researchers found that long-term exposure to air pollution has a consistent association with an increased risk of Alzheimer's disease. This association was somewhat stronger in individuals who had suffered a stroke. Hypertension and depression, however, had minimal additional impact. Specifically, only 1.6% of cases were mediated by hypertension, 2.1% by depression, and 4.2% by stroke.
"We found that long-term exposure to fine particles of polluted air is associated with an increased risk of Alzheimer's disease through direct effects on the brain, rather than through common chronic diseases," the authors of the study noted in a press release.
The link to stroke may be explained by the fact that already damaged cells are less able to protect the brain from toxic substances in the atmosphere.
"Our results suggest that individuals who have suffered a stroke may be particularly susceptible to the harmful effects of air pollution, highlighting an important intersection of environmental and vascular risk factors," the authors added.
The results showed that the pollution levels in the studied areas were on average about twice the limit set by the World Health Organization (WHO). The WHO recommends that the annual level of PM2.5—fine particles that penetrate deep into the lungs—should not exceed 5 micrograms per cubic meter of air.
PM2.5 can be formed outdoors from fuel combustion, construction work, and can consist of asphalt, soot, and other pollen particles. Such particles easily enter homes even through closed windows, and sometimes arise indoors, for example, during cooking.
According to statistical data for 2025, up to 7.2 million Americans aged 65 and older suffer from Alzheimer's disease. This is about 300,000 more cases than the previous year. In most cases, Alzheimer's disease manifests as dementia, characterized by impaired cognitive functions.
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