Air pollution increases the risk of developing neurological disorders like dementia, according to a new study led by researchers at Harvard T.H. Chan School of Public Health. The study reveals that prolonged exposure to fine particulate matter pollution (PM2.5), even at levels that are considered “safe,” is associated with a higher risk of first-time hospital admission for Parkinson’s disease, Alzheimer’s disease, and other types of dementia.
In collaboration with experts at Emory and Columbia University, the researchers conducted the first nationwide investigation into the link between neurodegenerative diseases and PM2.5 pollution in the United States. The long-term, comprehensive study was focused on more than 63 million older adults.
“The 2020 report of the Lancet Commission on dementia prevention, intervention, and care has added air pollution as one of the modifiable risk factors for these outcomes,” said study co-lead author Xiao Wu.
“Our study builds on the small but emerging evidence base indicating that long-term PM2.5 exposures are linked to an increased risk of neurological health deterioration, even at PM2.5 concentrations well below the current national standards.”
The researchers analyzed 17 years of hospital admissions data from 63,038,019 Medicare recipients and linked the cases with estimated PM2.5 concentrations by zip code.
The experts determined that for each increase in annual PM2.5 concentrations of 5 micrograms per cubic meter of air (μg/m3), there was a 13-percent greater risk of first-time hospitalization for Parkinson’s disease, Alzheimer’s disease, and related dementias. The risk of hospitalization for dementia was found to remain elevated at PM2.5 levels that are considered by EPA standards to be safe for human exposure.
The study showed that the link was most pronounced among urban populations, women, and Caucasians. For first-time Parkinson’s disease hospital admissions, the risk was highest in the northeastern United States, while the risk for first-time Alzheimer’s disease was highest among older adults in the Midwest.
“Our U.S.-wide study shows that the current standards are not protecting the aging American population enough, highlighting the need for stricter standards and policies that help further reduce PM2.5 concentrations and improve air quality overall,” said study co-senior author Antonella Zanobetti
The research is published in the journal The Lancet Planetary Health.