Exposure to hourly ambient temperature and temperature change between neighboring days and risk of emergency department visits for cause-specific cardiovascular disease

Little is known regarding the association between hourly exposure to ambient temperature and temperature change between neighboring days (TCN) with the risk of emergency department (ED) visits for cardiovascular disease (CVD). We conducted a time-stratified case-crossover study among 1.03 million ED visits for CVD between 2016 and 2021 in Zhejiang Province, China. Our analysis reported a reversed J-shaped relationship between hourly ambient temperature and risk of total and cause-specific CVD, with cold having the most significant effects. The risk associated with extreme cold (2.5^th percentile of temperature distribution) peaked approximately 40 h after exposure, while the effects of extreme heat (97.5^th percentile) were most pronounced during the concurrent hour of exposure (lag 0 h). Additionally, a decline in TCN (negative TCN) was associated with a higher risk of CVD, hypertensive disease, and stroke. In contrast, an increase in TCN (positive TCN) was associated with a lower risk of cause-specific CVD. The risks of negative and positive TCN peaked on the day of exposure and two days after exposure, respectively. These findings suggest that exposure to non-optimal temperature and TCN may increase the risk of ED visits for total and cause-specific CVD shortly after exposure, primarily driven by cold and negative TCN.