Risk of myocardial infarction and ischaemic stroke in adults with polymyositis and dermatomyositis: a general population-based study.

OBJECTIVE: Limited data are available on the risk of cardiovascular disease in DM and PM. The purpose of this study was to estimate the risk of incident myocardial infarction (MI) and ischaemic stroke in adults with incident PM/DM at the general population level.

METHODS: We assembled a retrospective cohort of all adults with incident PM/DM in British Columbia, and we matched up to 10 adults randomly selected from the general population. We estimated the incidence rates (IRs) per 1000 person-years for MI and stroke. We calculated hazard ratios (HRs), adjusting for potential confounders.

RESULTS: Among 774 new cases of inflammatory myopathies, 424 had PM (59% female, mean age 60 years) and 350 had DM (65% female, mean age 56 years). IRs for MI and stroke in PM were 22.52 and 10.15 events per 1000 person-years, respectively, vs 5.50 and 5.58 events in the comparison cohort, respectively. Fully adjusted HRs (95% CI) were 3.89 (95% CI: 2.28, 6.65) for MI and 1.76 (95% CI: 0.91, 3.40) for stroke. The age-, sex- and entry time-matched HRs for MI and stroke were highest in the first year after PM diagnosis (6.51, [95% CI: 3.15, 13.47] and 3.48 [95% CI: 1.26, 9.62], respectively). Similar trends were seen for DM.

CONCLUSION: Our study demonstrates that PM and DM are both associated with an increased risk of MI but not ischaemic stroke. Our findings support increased vigilance in cardiovascular prevention, surveillance and risk modification in adults with PM and DM.