Sex and age differences in the incidence of acute myocardial infarction during the COVID-19 pandemic in a Swedish health-care region without lockdown: a retrospective cohort study

Abstract

Summary: Background: The incidence of acute myocardial infarction has decreased during the COVID-19 pandemic, but sex and age differences in this change in incidence have not been tested. Thus, we aimed to compare the incidence of acute myocardial infarction in a health-care region in Sweden during the COVID-19 pandemic with previous years and to evaluate sex and age differences. Methods: We did a retrospective, observational cohort study using data from a national registry of patients admitted to coronary care units in Sweden. All patients admitted to one of three hospitals in Region Jönköping County with a diagnosis of acute myocardial infarction during the COVID-19 pandemic (March 1 to July 31, 2020) or reference period (March 1 to July 31, 2017–19) were included. The incidence of acute myocardial infarction (ST-elevation and non-ST-elevation) was calculated for both study periods. Participants were grouped according to sex and age (<70 years vs ≥70 years). The incidence and the incidence rate ratio (IRR) between the two study periods was calculated for each group and compared between groups using the Breslow-Day test. Findings: The study included 1088 participants, 846 who were admitted for acute myocardial infarction during the reference period and 242 who were admitted during the COVID-19 pandemic period. The IRR of acute myocardial infarction for the COVID-19 period compared with the reference period was 0·85 (95% CI 0·73–0·98). The IRR for acute myocardial infarction was significantly lower among women aged 70 years or older (0·56 [0·40–0·78]) than among men aged 70 years or older (0·97 [0·77–1·23]; p=0·0074). Interpretation: The incidence of acute myocardial infarction decreased predominantly among women aged 70 years or older during the COVID-19 pandemic. This highlights potential sex differences in health effects of the COVID-19 pandemic, which should be further elucidated. Funding: None.