A new study led by Emory University researcher Yanling Deng's team shows that older people who are long-term exposed to higher levels of air pollution are at a higher risk of developing Alzheimer's disease (AD). The research was published in the open access journal "PLOS Medicine" on February 17, 2026.
The report pointed out that Alzheimer's disease is one of the main causes of dementia, affecting approximately 57 million people worldwide. Previous research has linked air pollution to a risk factor for a variety of chronic problems, including high blood pressure, stroke and depression, which themselves are linked to dementia. But for a long time, the scientific community has not been clear: whether polluted air mainly indirectly increases the risk of dementia by inducing these chronic diseases, or whether it can cause more direct damage to the brain.
To answer this question, the research team analyzed data on more than 27.8 million beneficiaries aged 65 and older in the U.S. federal Medicare (Medicare) system, spanning 2000 to 2018. The study compared individuals' long-term air pollution exposure levels with their new Alzheimer's disease diagnoses and further examined whether comorbidities such as stroke, hypertension, and depression affected the association. The results showed that the higher the exposure to air pollution, the greater the risk of Alzheimer's disease, and this association showed a clear and consistent trend. Among comorbid factors, the increased risk of pollution-related Alzheimer's disease is more pronounced among people with a history of stroke. In contrast, high blood pressure and depression did not significantly strengthen the relationship between air pollution and Alzheimer's disease risk.
Researchers believe that air pollution may promote the occurrence of Alzheimer's disease mainly through direct biological effects on the brain, rather than necessarily through the "transmission" of common chronic diseases. At the same time, people who have had a stroke in the past may be more sensitive to the neurological damage caused by polluted air, suggesting an important intersection between environmental risks and vascular risks. The study also pointed out that improving air quality may play a role in reducing the risk of dementia in the elderly and protecting brain health.