From a University of Washington News Release, the Air Pollution and Dementia Study and Commentary cited below:
Using data from two large, long-running study projects in the Puget Sound region of Washington State— 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 University of Washington study, Rachel Shaffer, the lead author and whose PhD dissertation this was, found that 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 now Dr. Shaffer, who conducted the research as a doctoral student in the UW Department of Environmental & Occupational Health Sciences.
Rachel Shaffer et al. used the Adult Changes in Thought (ACT) cohort study based in Seattle to examine associations between exposures to fine particulate matter with a diameter ≤2.5μm (PM2.5) and incident all-cause dementia. Once a patient with dementia was identified, the researchers compared the average pollution exposure of each participant leading up to the age at which the dementia patient was diagnosed. Exposure data was based on the home address of the individuals and not activity levels or locations. The researchers also had to account for the different years in which these individuals were enrolled in the study, since air pollution has dropped significantly since the 1970’s when 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. One microgram per cubic meter difference in PM2.5 pollution is extremely small and subtle.
“We know dementia develops over a long period of time. It takes years —even decades — 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.”
Although not the first to report on this subject, and this study proved only correlation not causation, Bete Ritz and Yu Yu in their invited commentary state: “this study makes an important contribution to the field, “not only due to its size and careful exposure and outcomes assessment, but especially because it suggests that the cognitive health of even a low-risk, low-exposure population may be affected. “
As the researchers state: “Air pollution exposure is ubiquitous globally. Strong evidence links air pollutants to cardiovascular events and diabetes, both known to affect cognition in elders. However, data in support of the contributions of air pollution to aging-related cognitive decline are only just emerging (Paul et al. 2019). As exposures are chronic and affect large populations, even modest risks result in large numbers of cases (Kuenzli 2002).” So, as the particulate pollution from western wildfires moves east, mask up.
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, and Lianne Sheppard; Fine Particulate Matter and Dementia Incidence in the AdultPublished:4 August 2021CID: 087001https://doi.org/10.1289/EHP9018
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