This study aimed to compare the odds of acute coronary syndrome (ACS) in patients aged 18 to 40 years to patients older than 40 years with and without secondary diagnoses of systemic lupus erythematosus (SLE) or antiphospholipid antibody syndrome (APLS) while controlling for traditional cardiovascular (CV) risk factors.

Data were extracted from the National Inpatient Sample database from 2016 to 2018. The National Inpatient Sample was searched for hospitalizations of adult patients with ACS as the principal diagnosis, with and without SLE or APLS as secondary diagnoses. Age was divided categorically into 2 groups: adults aged 18 to 40 years and those older than 40 years. The primary outcome was the development of ACS. Multivariate logistic regression analyses were used to adjust for confounders.

There were 90,879,561 hospital discharges in the 2016 to 2018 database. Of those, 55,050 between the ages of 18 to 40 years and 1,966,234 aged older than 40 years were hospitalized with a principal diagnosis of ACS. Traditional CV risk factors were associated with ACS hospitalizations in both age groups. In multivariate analysis of the 18 to 40 years age group, both SLE (odds ratio, 2.18; 95% confidence interval, 1.814–2.625) and APLS (odds ratio, 2.18; 95% confidence interval, 1.546–3.087) were strongly associated with ACS hospitalizations. After the age of 40 years, there were no increased odds of ACS hospitalizations for SLE or APLS.

In the younger population, SLE and APLS were strongly associated with ACS hospitalizations in addition to the traditional CV risk factors. In the older age group, traditional CV risk factors dominated and diluted the effect of SLE and APLS.