Ambient Temperature Effect on Acute Myocardial Infarction by Risk Factors

A U-shaped relationship between temperature and acute myocardial infarction (AMI) was observed, but the risk factors were rarely included.The authors sought to examine AMI's cold and heat exposure after considering their risk groups.Daily data on ambient temperature, newly diagnosed AMI, and 6 known risk factors of AMI for the Taiwan population from 2000 to 2017 were created by linking 3 Taiwan national databases. Hierarchical clustering analysis was performed. Poisson regression was performed on the AMI rate with the clusters along with the daily minimum temperature in cold months (November-March) and the daily maximum temperature in hot months (April-October).There were 319,737 patients with new-onset AMI over 109.13 billion person-days, corresponding to the incidence rate of 107.02 per 100,000 person-years (95% CI: 106.64-107.39 person-years). Hierarchical clustering analysis identified 3 distinct clusters (1: age <50 years, 2: age ≥50 years without hypertension, and 3: mainly age ≥50 years with hypertension) with AMI incidence rates of 16.04, 105.13, and 388.17 per 100,000 person-years, respectively. Poisson regression revealed that below 15 °C, cluster 3 had the highest risk of AMI per 1°C reduce in temperature (slope = 1.011) compared with clusters 1 (slope = 0.974) and 2 (slope = 1.009). However, above the 32 °C thresholds, cluster 1 had the highest risk of AMI per 1 °C increase in temperature (slope = 1.036) compared with clusters 2 (slope = 1.02) and 3 (slope = 1.025). Cross validation showed a good fit for the model.People ≥50 years of age with hypertension are more susceptible to cold-related AMI. However, heat-related AMI is more prominent in individuals <50 years of age.