Long-Term Risk of Stroke in Myocardial Infarction Survivors: Thirty-Year Population-Based Cohort Study

Abstract

Background and purpose: Improved survival after myocardial infarction (MI) has increased the number of patients at risk of post-MI stroke. We examined risks of ischemic stroke, intracerebral hemorrhage (ICH), and subarachnoid hemorrhage (SAH) in patients with MI compared with the general population.

Methods: We conducted a nationwide population-based cohort study using Danish medical registries. During 1980 to 2009, we identified all patients with a first-time inpatient diagnosis of MI and formed a sex- and age-matched comparison cohort. We computed cumulative stroke risks and adjusted stroke rate ratios with 95% confidence intervals (CIs).

Results: We identified 258 806 patients with an MI and 1 244 773 individuals from the general population. For patients with MI, the cumulative stroke risks after 1 to 30 years were 12.6% for ischemic stroke, 1.2% for ICH, and 0.24% for SAH. During the first 30 days after MI, the adjusted stroke rate ratio was 30-fold increased for ischemic stroke (31.9; 95% CI, 28.4-35.8), 20-fold for ICH (21.8; 95% CI, 16.6-28.5), and 15-fold for SAH (16.6; 95% CI, 8.7-32.0). The adjusted stroke rate ratio remained increased during 31 to 365 days (3-fold for ischemic stroke, 2-fold for ICH, and 1.5-fold for SAH). During the ensuing 1 to 30 years, the risks remained increased for ischemic stroke (1.6; 95% CI, 1.6-1.6) but decreased to near unity for ICH (1.1; 95% CI, 1.0-1.2) and SAH (1.1; 95% CI, 0.94-1.2).

Conclusions: MI was a risk factor for all stroke subtypes during the first year of follow-up, but only for ischemic stroke thereafter.

Keywords: myocardial infarction; risk factor; stroke; subarachnoid hemorrhage.