Carbonaceous Components Underlying Wildfire Smoke PM2.5-Associated Alzheimer's Disease and Related Dementias in Older US Adults
- 1Emory Rollins School of Public Health
Abstract
Wildfire smoke exposure is increasing across the U.S., but the long-term neurological effects of smoke-specific fine particulate matter (PM2.5) and its carbonaceous components remain uncertain. Using Medicare data from 2002 through 2019, we examined incident Alzheimers disease (AD) and Alzheimers disease and related dementias (ADRD) among 39,678,630 fee-for-service Medicare beneficiaries followed from 2005 through 2019. We identified 3,501,414 incident AD cases over 258.5 million person-years and 8,377,416 incident ADRD cases over 248.6 million person-years. We linked the cohort with annual, high-resolution estimates of smoke and non-smoke PM2.5 mass and carbonaceous components (elemental and organic carbon) and fitted stratified Cox proportional hazards models. Per 1 {micro}g/m3 increase, smoke PM2.5 was associated with incident AD (hazard ratio [HR], 1.015, 95% confidence interval [CI], 1.005-1.026) and ADRD (1.029 [1.024-1.035]). Smoke carbonaceous fraction was also associated with AD (1.063 [1.042-1.085]) and ADRD (1.090 [1.077-1.103]). Within the ADRD endpoint, smoke-related associations exceeded their corresponding non-smoke associations on a per-unit-mass basis. Per interquartile range, associations were smaller for smoke PM2.5 (AD, 1.005 [1.002-1.008]; ADRD, 1.009 [1.008-1.011]) than for non-smoke PM2.5 (AD, 1.086 [1.079-1.094]; ADRD, 1.048 [1.043-1.053]). Associations varied across geographic, racial, socioeconomic, and clinical subgroups. Long-term wildfire smoke exposure, particularly its carbonaceous fraction, was associated with higher incidence of AD and ADRD among older U.S. adults. The associations correspond to 2,284 and 11,142 incident cases per year of AD and ADRD attributable to smoke PM2.5 among older Medicare beneficiaries, with the carbonaceous fraction accounting for most of this burden. These findings support the use of source-resolved and composition-specific smoke metrics in dementia research and wildfire-smoke health-impact assessments.
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BibTeX
@misc{jin2026carbonaceous,
title = {{Carbonaceous Components Underlying Wildfire Smoke PM2.5-Associated Alzheimer's Disease and Related Dementias in Older US Adults}},
author = {Z. Jin and K. Xu and M. Qi and Q. Zhu and B. Yang and G. A. Ferrada and J. S. Fu and N. Scovronick and H. H. Chang and A. Alonso and K. Steenland and Y. Liu},
howpublished = {medRxiv},
year = {2026},
month = oct,
doi = {10.64898/2026.10.08.26364863},
url = {https://www.medrxiv.org/content/10.64898/2026.10.08.26364863v1},
note = {CC BY-NC-ND},
}
RIS
TY - UNPB
TI - Carbonaceous Components Underlying Wildfire Smoke PM2.5-Associated Alzheimer's Disease and Related Dementias in Older US Adults
AU - Z. Jin
AU - K. Xu
AU - M. Qi
AU - Q. Zhu
AU - B. Yang
AU - G. A. Ferrada
AU - J. S. Fu
AU - N. Scovronick
AU - H. H. Chang
AU - A. Alonso
AU - K. Steenland
AU - Y. Liu
PY - 2026
DA - 2026/10/08
PB - medRxiv
DO - 10.64898/2026.10.08.26364863
UR - https://www.medrxiv.org/content/10.64898/2026.10.08.26364863v1
AB - Wildfire smoke exposure is increasing across the U.S., but the long-term neurological effects of smoke-specific fine particulate matter (PM2.5) and its carbonaceous components remain uncertain. Using Medicare data from 2002 through 2019, we examined incident Alzheimers disease (AD) and Alzheimers disease and related dementias (ADRD) among 39,678,630 fee-for-service Medicare beneficiaries followed from 2005 through 2019. We identified 3,501,414 incident AD cases over 258.5 million person-years and 8,377,416 incident ADRD cases over 248.6 million person-years. We linked the cohort with annual, high-resolution estimates of smoke and non-smoke PM2.5 mass and carbonaceous components (elemental and organic carbon) and fitted stratified Cox proportional hazards models. Per 1 {micro}g/m3 increase, smoke PM2.5 was associated with incident AD (hazard ratio [HR], 1.015, 95% confidence interval [CI], 1.005-1.026) and ADRD (1.029 [1.024-1.035]). Smoke carbonaceous fraction was also associated with AD (1.063 [1.042-1.085]) and ADRD (1.090 [1.077-1.103]). Within the ADRD endpoint, smoke-related associations exceeded their corresponding non-smoke associations on a per-unit-mass basis. Per interquartile range, associations were smaller for smoke PM2.5 (AD, 1.005 [1.002-1.008]; ADRD, 1.009 [1.008-1.011]) than for non-smoke PM2.5 (AD, 1.086 [1.079-1.094]; ADRD, 1.048 [1.043-1.053]). Associations varied across geographic, racial, socioeconomic, and clinical subgroups. Long-term wildfire smoke exposure, particularly its carbonaceous fraction, was associated with higher incidence of AD and ADRD among older U.S. adults. The associations correspond to 2,284 and 11,142 incident cases per year of AD and ADRD attributable to smoke PM2.5 among older Medicare beneficiaries, with the carbonaceous fraction accounting for most of this burden. These findings support the use of source-resolved and composition-specific smoke metrics in dementia research and wildfire-smoke health-impact assessments.
ER -