Critical Temperature Thresholds for Identifying Vulnerability to Heat‐Related Excess Cardiovascular Morbidity and Mortality

Background Extreme heat is a well‐established environmental hazard linked to elevated cardiovascular disease (CVD) morbidity and mortality, yet few studies evaluate temperature effects across multiple temporal scales or identify community‐specific vulnerability. Methods We analyzed neighborhood‐level CVD deaths and emergency department visits linked to sociodemographic characteristics and high‐resolution temperature and humidity estimates. Generalized additive models with smooth splines for temperature, humidity, age, and time estimated excess heat‐related rates across temporal scales. Principal component analysis and k‐means clustering classified Chicago community areas by multidimensional heat vulnerability. Results Higher temperatures were significantly associated with increased CVD and coronary heart disease mortality across warm‐season, monthly, and daily scales but were not associated with cardiovascular emergency department visits. Peak warm‐season thresholds for all CVD mortality occurred at 25.6 °C, corresponding to 20.7 excess deaths per 100 000 (SD 20.3; P