Air Pollution Linked to Higher Alzheimer’s Risk in Large-Scale Studies

Recent scientific research has examined the relationship between air pollution and the risk of Alzheimer’s disease in older adults, using large datasets from the United States and the United Kingdom. Findings from these studies provide new insights into how long-term exposure to fine particulate matter may affect brain health.

An Emory University study published in PLOS Medicine reviewed data from approximately 28 million U.S. Medicare beneficiaries aged 65 and older between 2000 and 2018. The analysis identified an association between long-term exposure to fine particulate air pollution (PM₂.₅) and an increased risk of developing Alzheimer’s disease, particularly among those with a prior history of stroke.

The same Emory University research indicated that many Alzheimer’s cases occurred independently of other chronic health conditions such as hypertension, stroke, and depression. This observation suggests a possible direct link between air pollution and the onset of Alzheimer’s disease that is not solely explained by other illnesses.

Further findings from the Emory team showed that the association between air pollution and Alzheimer’s risk was slightly stronger in people who had previously experienced a stroke. The study was published in the journal PLOS Medicine and focused on a large population of older Americans.

What the numbers show

• Data from over 27.8 million Medicare recipients aged 65 and older were analyzed
• A 3 µg/m³ difference in PM₂.₅ levels between cities was linked to a predicted 7 percent increase in Alzheimer’s incidence
• A UK Biobank study found exposure to PM₂.₅ ≥ 10 µg/m³ associated with a hazard ratio of 1.10 for all-cause dementia

Previous research from Emory University in 2021 also used Medicare data from 2000 to 2018 to investigate air pollution’s impact on dementia and Alzheimer’s disease. That study found that both PM₂.₅ and nitrogen dioxide (NO₂) were the strongest air pollutant risk factors, with no safe threshold identified even at low exposure levels such as 4 µg/m³.

International research has supported these findings. A UK Biobank cohort study involving 437,932 participants reported that exposure to PM₂.₅ levels at or above 10 µg/m³ was associated with a higher risk of all-cause dementia. The same study found that nitrogen oxides (NOx) at or above 50 µg/m³ were linked to increased risks of both all-cause dementia and Alzheimer’s disease.

The UK Biobank study also assessed genetic risk factors. Individuals with high genetic risk scores for Alzheimer’s disease who were exposed to higher NOx levels (≥ 50 µg/m³) showed an even greater risk of developing Alzheimer’s, with a hazard ratio of 1.36.

Across these studies, researchers found that air pollution is associated with increased risks of Alzheimer’s and dementia, regardless of the presence of other chronic conditions. The findings suggest that reducing exposure to air pollutants such as PM₂.₅ and NO₂ may be important for protecting brain health in older populations.

* This article is based on publicly available information at the time of writing.