Similar risk of cardiovascular events in idiopathic inflammatory myopathy and rheumatoid arthritis in the first 5 years after diagnosis

Objectives To estimate the incidence of cardiovascular (CV) events in idiopathic inflammatory myopathy (IIM) compared to patients with rheumatoid arthritis (RA) and the general population. To explore the contribution of traditional CV risk factors to any difference observed. Methods A retrospective matched population-based cohort study was conducted using UK Clinical Practice Research Datalink (CPRD) from 1987 to 2013. The incidence of CV events was calculated for each cohort over time and compared using Cox proportional hazards models. Multivariable analyses were used to adjust for traditional CV risk factors. Results A total of 603 patients with IIM 4047 RA and 4061 healthy controls were included. The rate of CV events in IIM was significantly greater than healthy controls [hazard ratio (HR) 1.47 (95% confidence interval (CI) 1.18-1.83)] and remained significant after adjustment for CV risk factors [HR 1.38 (95% CI 1.11-1.72)]. Risk was similar between IIM and RA [HR 1.01 (95% CI 0.78-1.31)]. The rate of myocardial infarction [HR 1.61 (95% CI 1.27-2.04)] but not stroke [HR 0.92 (95% CI 0.59-1.44)] was significantly greater in IIM compared to healthy controls. After the first 5 years, the rate of CV events for RA remained significantly greater compared to the control group, but appeared to return to that of the healthy controls in the IIM group. Conclusion IIM is associated with an increased risk of CV events in the first 5 years after diagnosis similar to that of RA. Beyond 5 years, the risk appears to return to that of the general population in IIM but not RA.