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

Abstract

ImportanceEmerging 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.ObjectiveTo examine associations of long-term exposure of total and source-specific PM2.5 with incident dementia in older adults.Design, Setting, and ParticipantsThe 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.ExposuresThe 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 MeasuresThe 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.ResultsAmong 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 RelevanceIn 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.

Neurometabolomic Impacts of Modeled Wildfire Smoke and Protective Benefits of Anti-Aging Therapeutics in Aged Female C57bl/6j Mice

“…Numerous epidemiological studies support a link between PM and neurological and behavioral health (10,71,72), but few have addressed wildfire smoke, specifically. A recent study, however, did note that risk of dementia from wildfire-derived PM was positive along with dusts from agricultural sources, while most other sources of PM were not associated with dementia outcomes (73).…”

Hypertension and Stroke as Mediators of Air Pollution Exposure and Incident Dementia

“…For example, particles are known to reach the brain through the olfactory, trigeminal, and vagus nerves and through peripheral circulation when breaching the blood-brain barrier, leading to local inflammation and oxidative stress . With observed associations of dementia in this cohort largely with PM 2.5 from agriculture, it may be that these direct pathways are most important due to neurotoxic compounds in pesticides entering the brain . Additionally, although the evidence is not conclusive, recent studies suggest that there are mediated pathways through mental health disorders (eg, depression), poor sleep quality, and insulin resistance or disruption of the normal action of insulin in the brain.…”

Are there place-based disparities in mortality risk? Findings from two longitudinal studies.

“…Census Bureau, 2010), two common features characterize rural versus urban places: (a) population count and (b) (non)adjacency to a metropolitan area (USDA Economic Research Service, 2019). Apart from differences in the sheer number of people located in rural versus urban areas, rural areas also tend to have reduced access to healthcare providers and services (Douthit et al, 2015; Gong et al, 2019; Johnston et al, 2019; Weinhold & Gurtner, 2014), fewer healthy amenities such as grocery stores and gyms (Losada-Rojas et al, 2021; Patterson et al, 2004), and worse water quality and air pollution (Hendryx et al, 2010; Strosnider et al, 2017; Zhang et al, 2023). For example, health professional shortages account for approximately 40% of the difference in preventable deaths across rural and urban areas (Johnston et al, 2019), and fine particulate matter (PM2.5; known to increase the risk for dementia) is most heavily emitted from agricultural sources and wildfires, which are more common in rural areas (Zhang et al, 2023).…”

“…Apart from differences in the sheer number of people located in rural versus urban areas, rural areas also tend to have reduced access to healthcare providers and services (Douthit et al, 2015; Gong et al, 2019; Johnston et al, 2019; Weinhold & Gurtner, 2014), fewer healthy amenities such as grocery stores and gyms (Losada-Rojas et al, 2021; Patterson et al, 2004), and worse water quality and air pollution (Hendryx et al, 2010; Strosnider et al, 2017; Zhang et al, 2023). For example, health professional shortages account for approximately 40% of the difference in preventable deaths across rural and urban areas (Johnston et al, 2019), and fine particulate matter (PM2.5; known to increase the risk for dementia) is most heavily emitted from agricultural sources and wildfires, which are more common in rural areas (Zhang et al, 2023). Furthermore, these environmental disadvantages are independent of polygenic risk for health problems (Davidson et al, 2022) and pose notable constraints on individuals’ capacity to engage in health-promoting behaviors like going to the doctor, exercising, and eating/drinking healthy (Matthews et al, 2017).…”