Fine particulate air pollution associated with higher risk of dementia


Date:
August 4, 2021
Source:
University of Washington
Summary:
Using data from two large, long-running study projects in the
Puget Sound region -- one that began in the late 1970s measuring
air pollution and another on risk factors for dementia that began
in 1994 -- researchers identified a link between air pollution
and dementia.



FULL STORY ========================================================================== Using data from two large, long-running study projects in the Puget Sound region -- one that began in the late 1970s measuring air pollution and
another on risk factors for dementia that began in 1994 -- University
of Washington researchers identified a link between air pollution and
dementia.


==========================================================================
In the UW-led study, a small increase in the levels of fine particle
pollution (PM2.5 or particulate matter 2.5 micrometers or smaller)
averaged over a decade at specific addresses in the Seattle area was
associated with a greater risk of dementia for people living at those addresses.

"We found that an increase of 1 microgram per cubic meter of exposure corresponded to a 16% greater hazard of all-cause dementia. There was
a similar association for Alzheimer's-type dementia," said lead author
Rachel Shaffer, who conducted the research as a doctoral student in the
UW Department of Environmental & Occupational Health Sciences.

"The ACT Study is committed to advancing dementia research by sharing
its data and resources, and we're grateful to the ACT volunteers who have devoted years of their lives to supporting our efforts, including their enthusiastic participation in this important research on air pollution,"
said Dr. Eric Larson, ACT's founding principal investigator and a senior investigator at KPWHRI.

The study, published Aug. 4 in the journal Environmental Health
Perspectives, looked at more than 4,000 Seattle-area residents enrolled
in the Adult Changes in Thought (ACT) Study run by Kaiser Permanente
Washington Health Research Institute in collaboration with UW. Of those residents, the researchers identified more than 1,000 people who had been diagnosed with dementia at some point since the ACT Study began in 1994.

Once a patient with dementia was identified, researchers compared the
average pollution exposure of each participant leading up to the age
at which the dementia patient was diagnosed. For instance, if a person
was diagnosed with dementia at 72 years old, the researchers compared
the pollution exposure of other participants over the decade prior to
when each one reached 72. In these analyses, the researchers also had to account for the different years in which these individuals were enrolled
in the study, since air pollution has dropped dramatically in the decades
since the ACT study began.



==========================================================================
In their final analysis, the researchers found that just a 1 microgram
per cubic meter difference between residences was associated with 16%
higher incidence of dementia. To put that difference into perspective,
Shaffer said, in 2019 there was approximately 1 microgram per cubic meter difference in PM2.5 pollution between Pike Street Market in downtown
Seattle and the residential areas around Discovery Park.

"We know dementia develops over a long period of time. It takes years
- - evendecades -- for these pathologies to develop in the brain, and
so we needed to look at exposures that covered that extended period,"
Shaffer said.

And, because of long-running efforts by many UW faculty and others
to build detailed databases of air pollution in our region, "we had
the ability to estimate exposures for 40 years in this region. That is unprecedented in this research area and a unique aspect of our study."
In addition to extensive air pollution and dementia data for the region,
other study strengths included lengthy address histories and high-quality procedures for dementia diagnoses for the ACT Study participants.

"Having reliable address histories let us obtain more precise air
pollution estimates for study participants," said senior author Lianne Sheppard, a UW professor of environmental and occupational health sciences
and of biostatistics. "These high-quality exposures combined with ACT's
regular participant follow-up and standardized diagnostic procedures
contribute to this study's potential policy impact." While there are many factors such as diet, exercise and genetics associated with the increased
risk of developing dementia, air pollution is now recognized to be among
the key potentially modifiable risk factors. The new UW-led results add
to this body of evidence suggesting air pollution has neurodegenerative
effects and that reducing people's exposure to air pollution could help
reduce the burden of dementia.

"How we've understood the role of air pollution exposure on health has
evolved from first thinking it was pretty much limited to respiratory
problems, then that it also has cardiovascular effects, and now there's evidence of its effects on the brain," said Sheppard, who this year was
awarded the Rohm & Haas Endowed Professorship of Public Health Sciences.

"Over an entire population, a large number of people are exposed. So, even
a small change in relative risk ends up being important on a population
scale," Shaffer said. "There are some things that individuals can do,
such as mask- wearing, which is becoming more normalized now because of
COVID. But it is not fair to put the burden on individuals alone. These
data can support further policy action on the local and national level
to control sources of particulate air pollution." Co-authors include
Magali Blanco, Joel Kaufman, Timothy Larson, Marco Carone, Adam Szpiro and
Paul Crane at UW; Ge Li at the VA Puget Sound Health Care System and UW;
Sara Adar at the University of Michigan; Eric Larson at the UW School
of Medicine and Kaiser Permanente Washington Health Research Institute.

This research was funded by multiple supporting grants from the National Institute for Environmental Health Sciences, National Institute on Aging,
UW Retirement Association Aging Fellowship, the Seattle chapter of the Achievement Rewards for College Scientists Foundation and others.

========================================================================== Story Source: Materials provided by University_of_Washington. Original
written by Jake Ellison. Note: Content may be edited for style and length.


========================================================================== Journal Reference:
1. Rachel M. Shaffer, Magali N. Blanco, Ge Li, Sara D. Adar, Marco
Carone,
Adam A. Szpiro, Joel D. Kaufman, Timothy V. Larson, Eric B. Larson,
Paul K. Crane, Lianne Sheppard. Fine Particulate Matter and Dementia
Incidence in the Adult Changes in Thought Study. Environmental
Health Perspectives, 2021; 129 (8): 087001 DOI: 10.1289/EHP9018 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2021/08/210804123113.htm

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