Abstract
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<0.001). Daily peaks occurred at 39.5 °C with 0.048 excess deaths per 100 000 per day (SD 0.068; P<0.001), and a 0 to 3-day lag peak at 38 °C produced 0.049 excess deaths per 100 000 (SD 0.133; P<0.001). Coronary heart disease mortality showed similar patterns, with warm-season peaks at 27.8 °C (9.19 per 100 000; P=0.004). No statistically significant associations were observed for myocardial infarction or stroke mortality. Principal component analysis and clustering identified 3 vulnerability profiles driven by socioeconomic disadvantage, racial and ethnic composition, heat exposure, and humidity. CONCLUSIONS: Temperature thresholds for cardiovascular mortality vary across temporal scales and CVD subtypes, with strongest associations for all CVD and coronary heart disease mortality. Integrating temperature-mortality relationships with community vulnerability profiles may support targeted heat warning systems and neighborhood-specific adaptation strategies.