What burns in a wildfire influences cardiovascular health outcomes: A systematic review and meta-analysis

The goal of this systematic review and meta-analysis is to understand cardiovascular health outcomes following wildfire and determine if fuel type clarifies variation in the association. The systematic review included English, peer-reviewed, primary data analysis studies that explored wildfire exposures with associated cardiovascular morbidity or mortality health outcomes published up to October 17, 2023 and identified through five databases (PROSPERO Protocol #CRD42024589994). We extracted article details, fire exposure metrics, cardiovascular health outcome metrics, study design, measures of association (risk ratio [RRs], incidence rate ratios [IRRs] and 95 % confidence intervals [CIs]), covariates, confounding factors, and stratified analyses from each article. Risk of bias was assessed using the Cochrane tool. Random effects meta-analyses, stratified by natural or structure/peat fuel types were conducted. Pooled estimates for all cardiovascular disease (pRR:1.04, 95 % CI: 1.01, 1.07), dysrhythmia (pRR:1.05, 95 % CI: 1.01, 1.09), and hypertensive disease (pRR:1.04, 95 % CI: 1.01, 1.07) were significantly associated with fire exposure. There were significant between group differences between wildfires with structure/peat sources compared to natural sources for all cardiovascular ED visits (RR structure/peat: 1.08, 95 % CI: 1.03, 1.12; RR natural: 1.03, 95 % CI: 1.00, 1.05) and dysrhythmia ED visits (RR structure/peat: 1.10, 95 % CI: 1.04, 1.09; RR natural: 1.02, 95 % CI: 0.98, 1.06). When exploring pooled estimates of risk for cardiovascular health, we find higher estimates and narrower CIs for structure/peat sources compared to natural wildfires with largely null estimates and wider CIs. Future detailed and consistent information about wildfire fuel types will help to inform better wildfire response.