Abstract
The number of myocardial infarctions declined during the early COVID-19 pandemic but mechanisms behind these declines are poorly understood. COVID-19 infection is also associated with an increased risk of myocardial infarction which could lead to higher incidence rates in the population. This study aims to shed light on the seemingly paradoxical relationship between COVID-19 and myocardial infarction occurrence on the population level by exploring long-term trends in incidence rates, case fatality, and proportion of patients dying before reaching a hospital. Our work is based on a linkage of administrative registers covering the entire population aged 60 + in Sweden. Considering both long-term trends since 2015 and seasonal variability, we compared observed incidence, case fatality, and proportions of patients hospitalized to expected values during 2020-2022. Despite more than 200 laboratory-confirmed COVID-19 cases per 1000 inhabitants by the end of 2022, incidence rates of myocardial infarction continued to decline, thus following the long-term trend observed already before 2020. During the first pandemic wave there was an additional incidence decline corresponding to 13% fewer myocardial infarctions than expected. This decline was neither accompanied by increasing case fatality nor by lower shares of patients being hospitalized. We found no increase in the population-level incidence of myocardial infarction despite large-scale exposure to COVID-19, which suggests that the effect of COVID-19 on myocardial infarction risk is not substantial. Increased pressure on the Swedish health care system has not led to increased risks or poorer outcomes for patients presenting with acute myocardial infarction.