Factors Underlying Reduced Hospitalizations for Myocardial Infarction During the COVID-19 Pandemic.

Importance: The incidence of hospital encounters for acute myocardial infarction (AMI) decreased sharply early in the COVID-19 pandemic and has not returned to prepandemic levels. There has been an ongoing debate about what mechanism may underlie this decline, including patients avoiding the hospital for treatment, excess mortality from COVID-19 among patients who would otherwise have had an AMI, a reduction in the incidence or severity of AMIs due to pandemic-related changes in behavior, or a preexisting temporal trend of lower AMI incidence.

Objective: To describe drivers of changing incidence in AMI hospital encounters during the COVID-19 pandemic.

Design, setting, and participants: This cross-sectional study used traditional Medicare claims from all patients enrolled in traditional Medicare from January 2016 to June 2023 (total of 2.85 billion patient-months) to calculate the rate of AMI hospital encounters (emergency department visits, observation stays, or inpatient admissions) per capita at all short-term acute care and critical access hospitals in the United States overall and by patient characteristics. Observed rates were compared with expected rates that accounted for shifts in population characteristics and the prepandemic temporal trend (as estimated over 2016-2019). Data were analyzed in November 2023.

Main outcomes and measures: Hospital encounters for AMI.

Results: On average, the study sample included 31 623 928 patients each month from January 2016 through June 2023, for a total of 2 846 153 487 patient-months during the 90-month study period. In June 2023, there were 0.044 AMI hospital encounters per 100 patients, which was 20% lower than in June 2019 (0.055 encounters per 100 patients). Early in the pandemic, AMI rates moved inversely with COVID-19 death rates and tracked patterns seen for other painful acute conditions, such as nephrolithiasis, suggesting these changes were associated with care avoidance. Changes in patient characteristics driven by excess deaths during the pandemic explained little of the decline. Later in the pandemic, the decline may be explained by the long-standing downward trend in AMI incidence; by April 2022, the observed rate of encounters matched the expected rate that accounted for this trend. During the full pandemic period, from March 2020 to June 2023, there were an estimated 5% (95% prediction interval, 1%-9%) fewer AMI hospital encounters than expected.

Conclusions and relevance: The early reduction in AMI encounters was likely driven by care avoidance, while ongoing reductions through June 2023 likely reflect long-standing temporal trends. During the pandemic, there were 5% fewer AMI encounters than expected.