Study pairs key air pollutants with home addresses to track progression of lost mobility through disability

(Press-News.org) ANN ARBOR—A University of Michigan study has taken a fine-grained, long-term look at residential-area air pollution and how it relates to deteriorating mobility—and hindered recovery—for older Americans.

By pairing and comparing the mobility and disability experiences of 29,790 participants in the national Health and Retirement Study with air quality exposures over 10 years, a team of veteran environmental health researchers found that people with long-term exposures were at greater risk of progressing from no physical function limitations to states of more physical function limitations and full disability over time.

The study zeroed in on nitrogen dioxide, ozone and fine particulate matter, the microscopic particles floating in the air, left behind by sources such as cars and diesel trucks, factories and agricultural operations, coal-fired power plants and wildfires.

"We found that higher residential air pollution levels were not only associated with faster declines in physical function, but also with reduced chances of recovery," said Sara Adar, senior author on the study published in JAMA's Network Open. Adar is a professor of epidemiology and global public health at the U-M School of Public Health. 

The pollutants found to be affecting the progression through mobility into disability have long been linked to inflammation in the body, respiratory disease, increased dementia risk and the worsening of other chronic illnesses. 

"Our results suggest that they may also play a role in worsening physical function with age," Adar said.

Adar worked on the study with lead author Jiaqi Gao of the University of Wisconsin and researchers from universities and medical schools across the country. 

"Our inquiry is unique in that we considered how exposure may hinder the reverse process toward recovery instead of focusing solely on the decline in physical functioning," Gao said. "Our study strengthens the evidence that air pollution is a modifiable risk factor for declining physical function, not only for disability but also for mobility."  

The study builds on previous research by following individuals' progression from health to limited mobility and disability, or in some cases, back to better health. 

"Our study shows that cleaner air may help people maintain physical function and even recover from setbacks, allowing them to stay stronger and more independent as they age," Adar said."We believe our research emphasizes that clean air is an important contributor to healthy aging."

The findings have potential clinical and societal significance given that the cost to the government to manage physical disabilities runs an estimated $400 billion annually, she said.

"Exposure to air pollution is not only a physical and emotional burden, it's also an economic one, increasing health care spending for the individuals affected, their families and taxpayers through higher Medicare spending, especially for people already with high health care needs," said Adar, whose research on air pollution and health care spending by older adults was recently published in Environment International.

 Researchers used responses from participants in the University of Michigan's landmark Health and Retirement Study, a large, long-running U.S. research study that tracks health, aging and economic conditions of adults 50 and older. The study is based at U-M's Institute for Social Research and funded by the National Institute on Aging.

To identify people living with mobility impairment, the researchers used study participants' responses to questions on difficulties performing any of five tasks for more than three months due to health problems: walking across a room, walking a block, walking several blocks, climbing one stair, climbing several stairs. 

To identify participants living with disabilities, they looked at survey questions that asked participants to self-report difficulty in any of six tasks over  three months due to health problems: bathing, eating, walking, dressing, toileting, and getting in and out of bed.

The pollutant measurements for the study came from the EPOCH, Environmental Predictors of Cognitive Health and Aging, database. The HRS is funded by the National Institute on Aging, NIA, while EPOCH is funded by the National Institute of Environmental Health Sciences and the NIA.

Co-authors on the study: Carlos Mendes de Leon, Georgetown University; Adam Szpiro and Joel Kaufman, University of Washington; Jennifer Weuve, Boston University; Kenneth Langa, Richard Hirth, Kelly Bakulski, Jen D'Souza, Jessica Faul, University of Michigan; Jinkook Lee, University of Southern California; Boya Zhang, Harvard University; Kayleigh Keller, Colorado State University.

Study: Air Pollution and the Progression of Physical Function Limitations and Disability and Aging Adults (DOI: 10.1001/jamanetworkopen.2025.58699)

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