Acute Coronary Syndrome in Idiopathic Inflammatory Myopathies: A Population-based Study

Objective. Evidence suggests an increased risk of cardiovascular (CV) diseases, including acute coronary syndrome (ACS), in idiopathic inflammatory myopathies (IIM). The aim of this study was to investigate the risk of ACS in an incident IIM cohort compared to the general Swedish population.

Methods. A cohort of 655 individuals with incident IIM and 6813 general population comparators were identified from national registries. IIM subjects were diagnosed from 2002 to 2011. Followup started at IIM diagnosis and corresponding date in the general population. ACS, CV comorbidities, and CV risk factors were defined using International Classification of Diseases codes. Incidence rates including 95% CI were calculated. Cox proportional hazards models were used to compare the risk of ACS in patients with IIM and the general population. The competing risk of death was accounted for using competing risk regression models.

Results. The incidence rate of ACS in IIM was higher than in the general population, particularly within the first year of diagnosis and in older individuals. The overall ACS incidence rate in IIM was 15.6 (95% CI 11.7–20.4) per 1000 person-years, with an HR of 2.4 (95% CI 1.8–3.2) compared with the general population. When accounting for the competing risk of death, the risk of ACS in IIM remained increased with a cumulative incidence of 7% at 5 years compared to 3.3% in the general population.

Conclusion. IIM individuals are at higher risk of ACS, particularly within the first year after diagnosis.