BackgroundWildfire smoke is known to exacerbate respiratory conditions; however, evidence for cardiovascular and cerebrovascular events has been inconsistent, despite biological plausibility.Methods and ResultsA populationâbased epidemiologic analysis was conducted for daily cardiovascular and cerebrovascular emergency department (ED) visits and wildfire smoke exposure in 2015 among adults in 8 California air basins. A quasiâPoisson regression model was used for zip codeâlevel counts of ED visits, adjusting for heat index, day of week, seasonality, and population. Satelliteâimaged smoke plumes were classified as light, medium, or dense based on modelâestimated concentrations of fine particulate matter. Relative risk was determined for smoky days for lag days 0 to 4. Rates of ED visits by ageâ and sexâstratified groups were also examined. Rates of allâcause cardiovascular ED visits were elevated across all lags, with the greatest increase on dense smoke days and among those aged â„65Â years at lag 0 (relative risk 1.15, 95% confidence interval [1.09, 1.22]). Allâcause cerebrovascular visits were associated with smoke, especially among those 65Â years and older, (1.22 [1.00, 1.49], dense smoke, lag 1). Respiratory conditions were also increased, as anticipated (1.18 [1.08, 1.28], adults >65 years, dense smoke, lag 1). No association was found for the control condition, acute appendicitis. Elevated risks for individual diagnoses included myocardial infarction, ischemic heart disease, heart failure, dysrhythmia, pulmonary embolism, ischemic stroke, and transient ischemic attack.ConclusionsAnalysis of an extensive wildfire season found smoke exposure to be associated with cardiovascular and cerebrovascular ED visits for all adults, particularly for those over aged 65 years.