Asger Risom
A study of more than 27 million older adults found that long-term exposure to fine particulate air pollution is directly associated with a higher risk of developing Alzheimer’s disease.
Long-term exposure to air pollution is directly associated with an increased risk of Alzheimer’s disease, according to a major US study analyzing data from more than 27 million older adults.
The research, published in PLOS Medicine, tracked people aged 65 and over between 2000 and 2018. During that period, around three million participants were diagnosed with Alzheimer’s disease.
Pollution and brain health
Researchers, led by a team from Emory University, examined exposure to fine particulate matter known as PM2.5 — microscopic particles produced by sources such as road traffic, power plants, industrial activity, wildfires, and household burning of fossil fuels and wood.
These particles are small enough to penetrate deep into the lungs and enter the bloodstream, potentially affecting multiple organs, including the brain.
Using residential zip codes to estimate pollution exposure, the study found that higher levels of PM2.5 were associated with a greater risk of developing Alzheimer’s disease.
Importantly, the researchers concluded that the link appears to be direct — not primarily explained by related conditions such as high blood pressure, stroke, or depression.
Stroke patients particularly vulnerable
While the association between pollution and Alzheimer’s was observed broadly, it was significantly stronger in people who had previously suffered a stroke.
The authors suggest that individuals with a history of stroke may be especially vulnerable to the neurological effects of air pollution, highlighting a possible interaction between environmental exposure and vascular damage.
Study limitations
The researchers acknowledged several limitations. Pollution exposure was estimated based on zip codes rather than exact home addresses, and only outdoor air pollution was considered. Indoor sources — such as cooking and home heating — were not included in the analysis.
Mark Dallas, a neuroscientist at the University of Reading who was not involved in the study, said the findings align with growing evidence that air pollution may be a modifiable risk factor for dementia.
A growing global burden
According to the World Health Organization, more than 55 million people worldwide are living with dementia, with Alzheimer’s disease accounting for up to 70% of cases.
In Europe alone, an estimated 12.1 million people were living with dementia in 2025, around two-thirds of them women.
The WHO introduced updated global air quality guidelines in 2021, and a 2025 action plan calls for a 50% reduction in air pollution-related mortality by 2040 compared with 2015 levels.
The study’s authors and independent experts say that reducing exposure to air pollution could play a meaningful role in protecting brain health and lowering dementia risk.
Sources: PLOS Medicine, News.ro, World Health Organization
