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Original Investigation
August 14, 2023

Comparison of Particulate Air Pollution From Different Emission Sources and Incident Dementia in the US

Author Affiliations
  • 1Department of Epidemiology, University of Michigan School of Public Health, Ann Arbor
  • 2Department of Epidemiology, Boston University School of Public Health, Boston, Massachusetts
  • 3Institute for Social Research, University of Michigan, Ann Arbor
  • 4University of Michigan Medical School, Ann Arbor
  • 5Institute for Healthcare Policy and Innovation, University of Michigan, Ann Arbor
  • 6Veterans Affairs Center for Clinical Management Research, Ann Arbor, Michigan
  • 7Department of Biostatistics, University of Washington, Seattle
  • 8Department of Oncology, Georgetown University, Washington, DC
  • 9Department of Epidemiology, University of Washington, Seattle
  • 10Department of Environmental and Occupational Health Sciences, University of Washington, Seattle
  • 11Department of Medicine, University of Washington, Seattle
  • 12Center for Economic and Social Research, University of Southern California, Los Angeles
  • 13Department of Health Management and Policy, University of Michigan School of Public Health, Ann Arbor
  • 14Department of Internal Medicine, University of Michigan, Ann Arbor
JAMA Intern Med. 2023;183(10):1080-1089. doi:10.1001/jamainternmed.2023.3300
Key Points

Question  Are long-term exposures to particulate air pollution from different emission sources associated with incident dementia?

Findings  In this nationally representative cohort study in the US, higher residential levels of fine particulate matter were associated with greater rates of incident dementia, especially for fine particulate matter generated by agriculture and wildfires.

Meaning  These findings support the hypothesis that airborne particulate matter pollution is associated with the likelihood of developing dementia and suggest that selective interventions to reduce pollution exposure may decrease the life-long risk of dementia; however, more research is needed to confirm these relationships.


Importance  Emerging evidence indicates that exposure to fine particulate matter (PM2.5) air pollution may increase dementia risk in older adults. Although this evidence suggests opportunities for intervention, little is known about the relative importance of PM2.5 from different emission sources.

Objective  To examine associations of long-term exposure of total and source-specific PM2.5 with incident dementia in older adults.

Design, Setting, and Participants  The Environmental Predictors of Cognitive Health and Aging study used biennial survey data from January 1, 1998, to December 31, 2016, for participants in the Health and Retirement Study, which is a nationally representative, population-based cohort study in the US. The present cohort study included all participants older than 50 years who were without dementia at baseline and had available exposure, outcome, and demographic data between 1998 and 2016 (N = 27 857). Analyses were performed from January 31 to May 1, 2022.

Exposures  The 10-year mean total PM2.5 and PM2.5 from 9 emission sources at participant residences for each month during follow-up using spatiotemporal and chemical transport models.

Main Outcomes and Measures  The main outcome was incident dementia as classified by a validated algorithm incorporating respondent-based cognitive testing and proxy respondent reports. Adjusted hazard ratios (HRs) were estimated for incident dementia per IQR of residential PM2.5 concentrations using time-varying, weighted Cox proportional hazards regression models with adjustment for the individual- and area-level risk factors.

Results  Among 27 857 participants (mean [SD] age, 61 [10] years; 15 747 [56.5%] female), 4105 (15%) developed dementia during a mean (SD) follow-up of 10.2 [5.6] years. Higher concentrations of total PM2.5 were associated with greater rates of incident dementia (HR, 1.08 per IQR; 95% CI, 1.01-1.17). In single pollutant models, PM2.5 from all sources, except dust, were associated with increased rates of dementia, with the strongest associations for agriculture, traffic, coal combustion, and wildfires. After control for PM2.5 from all other sources and copollutants, only PM2.5 from agriculture (HR, 1.13; 95% CI, 1.01-1.27) and wildfires (HR, 1.05; 95% CI, 1.02-1.08) were robustly associated with greater rates of dementia.

Conclusion and Relevance  In this cohort study, higher residential PM2.5 levels, especially from agriculture and wildfires, were associated with higher rates of incident dementia, providing further evidence supporting PM2.5 reduction as a population-based approach to promote healthy cognitive aging. These findings also indicate that intervening on key emission sources might have value, although more research is needed to confirm these findings.

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1 Comment for this article
Climate geoengineering, PM2.5, and dementia
Giovanni Ghirga, Pediatrician | International Society of Doctors for the Environment (Italy)
This interesting research brings about a deep reflection on interventions aimed at slowing down global warming.
In the realm of climate change mitigation, geoengineering technologies have sparked both curiosity and concern. One proposed method, global stratospheric aerosol injection, aims to counteract rising global temperatures by releasing substances, such as sulphate aerosols, into the lower stratosphere to reflect sunlight back into space. A recent analysis delved into the potential consequences of implementing this technology, comparing it with scenarios involving uncontrolled climate change.
Findings of this study revealed an increase in mortality rates due to elevated levels of PM2.5 sulphate particles
as a result of this geoengineering approach. Furthermore, there could be a potential rise in dementia incidence associated with the increased concentration of PM2.5 particles resulting from stratospheric aerosol injection.
The potential link between PM2.5 particles and an increase in dementia cases raises additional concerns about the unintended consequences of this particular geoengineering technique.

Tracy SM, Moch JM, Eastham SD, Buonocore JJ. Stratospheric aerosol injection may impact global systems and human health outcomes. Elementa: Science of the Anthropocene. 2022;10(1):00047. doi:10.1525/elementa.2022.00047.