Study Finds Significant Link Between Air Pollution and Neurological Disorders

Environmental Health Scientist is co-senior author of the first nationwide analysis of the link between fine particulate (PM2.5) pollution and neurodegenerative diseases in the U.S

October 20, 2020

Air pollution was significantly associated with an increased risk of hospital admissions for several neurological disorders, including Parkinson’s disease, Alzheimer’s disease, and other dementias, in a long-term study of more than 63 million older U.S. adults. The research was conducted by Harvard T.H. Chan School of Public Health, and colleagues at Columbia University Mailman School of Public Health, and Emory University’s Rollins School of Public Health

The study, the first nationwide analysis of the link between fine particulate (PM2.5) pollution and neurodegenerative diseases in the U.S, is published in The Lancet Planetary Health. The researchers leveraged an unparalleled amount of data compared to any previous study of air pollution and neurological disorders.

“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 Xiao Wu, a doctoral student in biostatistics at Harvard Chan School and co-lead author of the study. “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.” 

Researchers looked at 17 years’ worth (2000–2016) of hospital admissions data from 63,038,019 Medicare recipients in the U.S. and linked these with estimated PM2.5 concentrations by ZIP code. Taking into account potential confounding factors like socioeconomic status, they found that, for each 5 microgram per cubic meter of air (μg/m3) increase in annual PM2.5 concentrations, there was a 13% increased risk for first-time hospital admissions both for Parkinson’s disease and for Alzheimer’s disease and related dementias. This risk remained elevated even below supposedly safe levels of PM2.5 exposure, which, according to current U.S. Environmental Protection Agency standards, is an annual average of 12 μg/m3 or less.

Women, white communities, and urban populations were particularly susceptible, the study found. The highest risk for first-time Parkinson’s disease hospital admissions was among older adults in the northeastern U.S. For first-time Alzheimer’s disease and related dementias hospital admissions, older adults in the Midwest faced the highest risk. 

“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 Antonella Zanobetti, PhD, principal research scientist in Harvard Chan School’s Department of Environmental Health and a co-senior author of the study.

“As the American population is aging, the number of people with Parkinson's and Alzheimer's diseases is expected to increase,” said Marianthi-Anna Kioumourtzoglou, ScD, assistant professor in environmental health sciences at Columbia Mailman School, and a co-senior author. “We found that particulate air pollution is an important factor contributing to disease aggravation, even at levels below the current national standards. To best protect older Americans, therefore, stricter standards are warranted.”

Other authors included Mahdieh Danesh Yazdi, Danielle Braun, Yaguang Wei, Yun Wang, Joel Schwartz, and Francesca Dominici, Liuhua Shi, Yara Abu Awad, Yaguang Wei, Pengfei Liu, and Qian Di. 

The study was supported by the Health Effects Institute (4953-RFA14-3/16-4), the National Institute of Environmental Health Sciences (NIEHS R01 ES024332, R01 ES028805, R21 ES028472, P30 ES009089, P30 ES000002), the National Institute on Aging (NIA/NIH R01 AG066793-01, P50 AG025688), and the HERCULES Center (P30ES019776). Research described in this article was done under contract to the Health Effects Institute, an organization jointly funded by the U.S. Environmental Protection Agency (assistance award number R-83467701) and some motor vehicle and engine manufacturers.

Marianthi-Anna Kiomourtzoglou is an assistant professor at Columbia Mailman School of Public Health studying statistical issues related to environmental epidemiology. Read more of her past work, such as a study linking the Pregnancy Drug DES to ADHD in Users’ Grandchildren.