People exposed to higher levels of air pollution may face an increased risk of developing Alzheimer’s disease, according to a new study published in PLOS Medicine. Researchers found that fine particulate matter (PM₂.₅), a common pollutant from vehicle emissions, industrial activity, power plants, wildfires, and household fuel use, can affect the brain directly, rather than only through other chronic health conditions.
The study, led by a team at Emory University in the United States, analysed health data from more than 27 million people aged 65 and older between 2000 and 2018. Around three million participants developed Alzheimer’s during this period. Researchers also examined the role of three common comorbidities—hypertension, stroke, and depression—to see whether they influenced the onset of dementia in polluted environments.
The findings showed a significant link between air pollution and Alzheimer’s, independent of these other conditions. The association was strongest among individuals with a history of stroke, suggesting that vascular factors may heighten the brain’s vulnerability to pollution. “Our findings suggest that individuals with a history of stroke may be particularly vulnerable to the harmful effects of air pollution on brain health, highlighting an important intersection between environmental and vascular risk factors,” the authors said.
Long-term exposure to PM₂.₅ has previously been linked to cardiovascular disease, high blood pressure, and mental health disorders. Fine particles are especially harmful because they can penetrate deep into the lungs and enter the bloodstream, potentially reaching the brain.
The study did have limitations. Air pollution exposure was measured at the postcode level rather than individual addresses, and only outdoor levels were included, leaving out indoor sources such as cooking and heating. Despite these constraints, experts say the results add to growing evidence that air pollution is a modifiable risk factor for dementia.
“Because the research relies on broad pollution estimates and medical records, there are important limitations, but the findings align with growing evidence that air pollution is a modifiable risk factor for dementia,” said Mark Dallas, a professor at the University of Reading who was not involved in the study. He added that the findings underscore the long-term impact of the air people breathe on brain health.
Efforts to reduce air pollution are underway in many countries, but most are unlikely to meet global targets by 2030. The World Health Organization’s 2025 roadmap calls for a 50 percent reduction in mortality from air pollution, mainly targeting fine particulate matter, by 2040 compared with 2015 levels. Sheona Scales, director of research at Alzheimer’s Research UK, said the study highlights the global importance of reducing exposure. “Setting stronger, health-based air quality targets and reducing exposure would help protect our brains as well as our lungs and could lower the overall risk of dementia,” she said.
Alzheimer’s disease accounts for up to 70 percent of dementia cases, affecting more than 55 million people worldwide. In Europe, roughly 12.1 million people were living with dementia in 2025, with women making up about two-thirds of cases. As populations age, these numbers are expected to rise, making the need for environmental and health interventions more urgent.
