To Örebro University

OBJECTIVE: To study the occurrence of ischemic stroke and hemorrhagic stroke in patients with idiopathic inflammatory myopathies (IIMs) compared to that in the general population and to investigate how it varies by sex, age, clinical subdiagnosis, and time since IIM diagnosis.

METHODS: All patients in Sweden with newly diagnosed IIM were identified from the National Patient Register, and general population comparators were identified from the Total Population Register. The study population was followed prospectively until death, emigration, December 2013, or first incident stroke. Incidence rates, rate differences, and hazard ratios (HRs) comparing patients with IIMs to the general population were estimated and stratified by age, sex, type of IIM, and time since diagnosis. To account for the competing risk of death, the subdistribution HR was estimated using Fine and Gray models.

RESULTS: We observed 34 and 229 stroke events in 663 IIM patients and 6,673 comparators, respectively. The HR was elevated for ischemic stroke (HR 2.1 [95% confidence interval (95% CI) 1.4, 3.0]). Few hemorrhagic stroke events were identified, but an increased risk was observed (HR 1.9 (95% CI 0.7, 5.5]). The association remained elevated for both outcomes when taking the competing risk of death into account. For ischemic stroke, the rate difference was highest in the oldest age group (≥68 years), while the HR was highest in the youngest age group (<56 years).

CONCLUSION: Our findings indicate that the risk of both ischemic stroke and hemorrhagic stroke is increased in patients with IIMs, but it should be kept in mind that stroke is a rare event. Focus on prevention should be directed toward groups with the highest absolute risk, especially older patients.