Influence of seasons on the management and outcomes acute myocardial infarction: An 18-year US study

Background: There are limited data on the seasonal variation in acute myocardial infarction (AMI) in the contemporary literature. Hypothesis: There would be decrease in the seasonal variation in the management and outcomes of AMI. Methods: Adult (>18 years) AMI admissions were identified using the National Inpatient Sample (2000-2017). Seasons were classified as spring, summer, fall, and winter. Outcomes of interest included prevalence, in-hospital mortality, use of coronary angiography, and percutaneous coronary intervention (PCI). Subgroup analyses for type of AMI and patient characteristics were performed. Results: Of the 10 880 856 AMI admissions, 24.3%, 22.9%, 22.2%, and 24.2% were admitted in spring, summer, fall, and winter, respectively. The four cohorts had comparable age, sex, race, and comorbidities distribution. Rates of coronary angiography and PCI were slightly but significantly lower in winter (62.6% and 40.7%) in comparison to the other seasons (64-65% and 42-43%, respectively) (P <.001). Compared to spring, winter admissions had higher in-hospital mortality (adjusted odds ratio [aOR]: 1.07; 95% confidence interval [CI]: 1.06-1.08), whereas summer (aOR 0.97; 95% CI 0.96-0.98) and fall (aOR 0.98; 95% CI 0.97-0.99) had slightly lower in-hospital mortality (P <.001). ST-segment elevation (10.0% vs 9.1%; aOR 1.07; 95% CI 1.06-1.08) and non-ST-segment elevation (4.7% vs 4.2%; aOR 1.07; 95% CI 1.06-1.09) AMI admissions in winter had higher in-hospital mortality compared to spring (P <.001). The primary results were consistent when stratified by age, sex, race, geographic region, and admission year. Conclusions: Compared to other seasons, winter admission was associated with higher in-hospital mortality in AMI in the United States.