Strong Link between Air Pollution and Hospital Admission for Neurological Disorders

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Neurological Disorders: The risk of hospital admission for Parkinson’s disease or Alzheimer’s disease and related dementias significantly increases with rising air pollution levels. The risk is greater for some sections of the population, such as women, white people, and people living in urban areas.

According to the first-ever nationwide analysis study published in The Lancet Planetary Health searching for a link between fine particulate (PM2.5) pollution and neurodegenerative diseases in the U.S, air pollutants might increase neurodegeneration risk because some air pollutants, including fine particulate matter, cross the blood-brain barrier into the brain, where they could have toxic effects. The researchers leveraged an unparalleled amount of data compared to any previous study of air pollution and neurological disorders. Xiao Wu, a doctoral student in biostatistics at Harvard Chan School and co-lead author of the study, said:

“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. 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.” 

PM2.5 Concentrations

The long-term study involved senior adults in the United States and considered 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. 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 researchers took into account potential confounding factors like socioeconomic factors. They found that for every 5 micrograms 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 high even below what is considered 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. The study found that women, white people, and urban populations were particularly susceptible. Marianthi-Anna Kioumourtzoglou, ScD, assistant professor in environmental health sciences at Columbia Mailman School and a co-senior author, said:

“As the American population is aging, the number of people with Parkinson’s and Alzheimer’s diseases is expected to increase […] 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.”

Impair Your Memory  | Neurological Disorders

There’s overwhelming evidence that air pollution causes lung cancer, chronic obstructive pulmonary disease, emphysema, asthma, heart disease, and stroke. One recent study in China estimated that for those ages 75 and older, there are 1,166 early deaths for every 100,000 people — that’s more than 1%. It is now clear that if it doesn’t kill you outright, air pollution can impair your memory and cause dementia in general and Alzheimer’s disease, one cause of dementia in particular.

Researchers can now join the dots and explain what happens to your brain when you breathe in polluted air and how it can lead to neurodegeneration years later. When you inhale pollutants, the smallest particles emitted by cars, power plants, and other places where fuel is burned lodge in your lungs’ sensitive tissue or pass into your bloodstream. The pollutants trigger an immune response where it seeks to trap, contain, and remove invading particles. In time that response generalizes to systemic inflammation or an overactive, overly excited immune response across the body.

Existing Air Pollution Standards

Motivated, in part, by the new evidence, researchers increasingly see dementia as a disease like cancer, where multiple factors could lead to pathology. Unlike smoking, we can’t always know when we are being exposed to dirty air, and we can’t decide when to quit. Yet the researchers firmly believe that we could avoid more dementia by strengthening our existing air pollution standards. Antonella Zanobetti, Ph.D., a principal research scientist at Harvard Chan School’s Department of Environmental Health and a co-senior author of the study, concludes: 

“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.”