Research led by Emory University suggests that direct exposure to fine particulate matter pollution, or PM2.5, increases a person’s risk of developing Alzheimer’s disease.
Alzheimer’s disease is the most frequent type of dementia and affects roughly 57 million people around the globe. As explained in PLOS Medicine, both air pollution and other health conditions or events, such as high blood pressure, stroke, and depression, are linked to increased risk for the neurodegenerative condition.
“However, whether these comorbidities mediate or amplify the effects of PM2.5 on Alzheimer’s disease remains unclear,” wrote lead investigator and first author Yanling Deng, PhD, a researcher at Emory, and colleagues.
To try to clarify this confusion, Deng and colleagues carried out a study including 27.8 million Medicare beneficiaries aged 65 years or older between 2000 and 2018. High-resolution data recording PM2.5 exposure levels across the United States was linked to the residential address of the participants to evaluate their level of exposure.
Information about diagnosis of Alzheimer’s disease across the cohort and possible links with other health problems was also assessed by the researchers.
Overall, around three million cases of Alzheimer’s disease were diagnosed during the study period. PM2.5 exposure during the five years preceding diagnosis was directly linked to Alzheimer’s.
The team found a small but significant 8.5% increase in risk for developing Alzheimer’s disease during the next five years if people moved from a low pollution area (estimated PM2.5 level of around 8.2 μg/m³) to a high pollution area (estimated PM2.5 level of approximately 12.0 μg/m³).
Looking at the impact of stroke, depression, and high blood pressure, the increase in Alzheimer’s risk linked to a move from a low to a high PM2.5 exposure went up slightly in people with past stroke to around 11%, but depression and high blood pressure did not seem to significantly influence the effect of air pollution.
“Although all three comorbidities, including hypertension, stroke, and depression, were associated with both PM2.5 exposure and Alzheimer’s disease risk, the effect of air pollution was largely independent of the presence of comorbidities, which did not act as mediators,” the authors said.
“Our findings suggest that reducing air pollution could benefit cognitive health broadly across older adults, while targeted interventions may be especially important for those with cerebrovascular disease or multiple chronic conditions,” they concluded.
