People with greater exposure to air pollution may have a higher risk of developing Alzheimer’s, according to a new study.
People with greater exposure to air pollution face a higher risk of developing Alzheimer’s disease, a new study has found.
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Exposure to air pollution is a known risk factor for Alzheimer’s disease and for several common chronic health conditions, such as hypertension, stroke, and depression.
These chronic conditions are also linked to Alzheimer’s disease, and previously, it was unclear whether air pollution causes these chronic conditions, which then lead to dementia, or if these conditions might amplify the brain damage from air pollution.
A new study published in PLOS Medicine found that exposure to air pollution was associated with an increased risk of Alzheimer’s disease.
The research team at Emory University in the United States (US) analysed data from more than 27 million people aged 65 or older from 2000 to 2018 – around three million people developed Alzheimer’s during the study.
At the same time, they analysed the burden of three common comorbidities – hypertension, stroke, and depression – to see if they played a role in the onset of Alzheimer's.
Researchers compared these results to the levels of fine particulate air pollution (PM₂.₅) to which participants were exposed, depending on where they lived.
Fine particulate matter is hazardous because it can penetrate deep into the lungs and the bloodstream. Common sources include vehicle emissions, power plants, industrial activities, wildfires, and household burning of wood or fossil fuels.
The research found that air pollution affected the brain through direct effects rather than through other chronic conditions, the authors noted.
The link between air pollution and Alzheimer's was stronger among people who had had a stroke.
“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 of the study said.
Long-term exposure to particulate matter has also been shown to increase the risk of chronic diseases such as cardiovascular conditions, hypertension, and mental health disorders.
The study had some limitations. Air pollution levels were measured by postcode instead of by individual addresses. Only outdoor levels were measured, meaning it didn’t account for cooking, heating, and other potential particulate sources.
“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 from the University of Reading, who did not participate in the study.
He added that, overall, the study reinforces a simple idea: the air people breathe over many years can shape how brains age.
Tackling air pollution
Many countries worldwide have targets to reduce air pollution levels. Still, the majority of them will struggle to reach the right numbers by 2030.
Global targets for particulate matter are defined by the World Health Organization's 2021 Global Air Quality Guidelines (AQGs).
The 2025 WHO roadmap, approved by the World Health Assembly, targets a 50 percent drop in air pollution mortality, largely driven by fine particulate matter, by 2040 compared to the baseline in 2015.
“The implications for this US study are global. Air pollution is a challenge we need to tackle together. 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”, said Sheona Scales, director of research at Alzheimer’s Research UK, who was not part of the research.
Alzheimer’s is increasing worldwide
More than 55 million people live with dementia globally, with Alzheimer’s disease accounting for up to 70 percent of cases, according to the World Health Organisation.
In 2025, approximately 12.1 million people were living with dementia in Europe, with women disproportionately affected, comprising about 66 percent of cases.
Driven by ageing populations, numbers worldwide are projected to increase.
