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TOPLINE:

Among older adults in the western United States, exposure to high concentrations of smoke-related fine particulate matter (PM2.5) was associated with increased rates of hospitalizations for respiratory diseases, with weaker but suggestive ties to cardiovascular hospitalizations.

METHODOLOGY: 

• Researchers carried out a retrospective cohort study to analyze the association between exposure to smoke-specific PM2.5 and cause-specific hospitalizations in older adults in the United States.
• They used inpatient claims data of 10,369,361 Medicare beneficiaries (mean age, 74.7 years; 53.1% women) across 11 western United States during wildfire seasons from 2006 to 2016, with 57,974,120 person-months of follow-up.
• The causes of unscheduled hospitalizations were inferred from International Classification of Diseases, Ninth Revision, Clinical Modification codes and classified into various disease categories.
• Daily concentrations of surface-level smoke-specific PM2.5 were estimated through machine learning models that utilized ground measurements, satellite data, and reanalysis data sources.
• The associations between causes of hospitalization and smoke-specific PM2.5 were characterized by examining daily county-level rates of unscheduled hospitalization by disease category, modeling hospitalization rates according to same-day and prior-week smoke-specific PM2.5 exposure.

TAKEAWAY:

• The leading cause of unscheduled hospitalizations was cardiovascular disease, with a mean daily rate of 7.92 per 100,000 persons, followed by digestive system disease at 3.62 and respiratory disease at 3.53 per 100,000 persons.
• Respiratory hospitalizations increased as smoke-specific PM2.5 exceeded 25 μg/m³, with average daily rates increasing by 2.40 (95% CI, 0.17-4.63) per 100,000 persons when PM2.5 levels rose from 0 to 40 μg/m³ over a week.
• Hospitalizations due to cardiovascular diseases were unrelated to smoke-specific PM2.5 at exposure levels < 20 μg/m³ but showed an increasing trend at higher concentrations.
• No significant associations were seen for hospitalizations related to injuries, digestive issues, neuropsychiatric conditions, or endocrine disorders.

IN PRACTICE:

“This information can be used by both policymakers and clinicians to design policies and guidelines to protect vulnerable older adults from the escalating health threats posed by wildfire smoke,” the authors wrote.

SOURCE:

This study was led by Sofia L. Vega, Harvard T.H. Chan School of Public Health, Boston. It was published online on April 30, 2025, in JAMA Network Open.

LIMITATIONS:

Estimating concentrations of smoke-specific PM2.5 proved challenging due to the lack of direct measurements. County-level exposure measures may not have accurately reflected the exposures experienced by individual residents. This study did not include information on wildfires from recent years when their intensity increased.

DISCLOSURES:

This study was supported by the Harvard Climate Change Solutions Fund and grants from the National Institutes of Health. One author reported receiving support through an environmental fellowship at the Harvard University Center. The authors reported having no conflicts of interest.

This article was created using several editorial tools, including AI, as part of the process. Human editors reviewed this content before publication.