Long-term risk of seizures among cardiac arrest survivors

Abstract

Introduction: The long-term risk of seizures in cardiac arrest survivors is not established. We hypothesized that survivors of cardiac arrest face an increased long-term risk for seizures.

Methods: We performed a retrospective cohort study using 2008-2015 claims data from a nationally representative 5% sample of Medicare beneficiaries ≥66 years-old. Our exposure of interest was a hospital diagnosis code of cardiac arrest, defined by previously validated ICD-9-CM codes. Since we were interested in long-term risk, we excluded patients with a history of seizure, and those who were diagnosed with a seizure during hospitalization or died during the index hospitalization. Our outcome was a diagnosis of seizure. Survival statistics were used to calculate seizure incidence and Cox proportional hazards models were used to determine the association between cardiac arrest and long-term seizures after adjustment for demographics and Charlson comorbidities.

Results: Among 1,764,508 beneficiaries with a mean 4.5 years of follow-up, we identified 57,437 patients with cardiac arrest who survived to discharge without a seizure. The annual incidence of seizures was 1.26% (95% confidence interval [CI], 1.20-1.33%) compared to 0.61% (95% CI, 0.61-0.62%) in other Medicare patients. In unadjusted analysis, cardiac arrest was associated with an increased risk of post-discharge seizures (hazard ratio [HR], 1.8; 95% CI, 1.7-1.9), but the association was lost after adjustment for demographics and comorbidities (HR 0.9; 95% CI, 0.9-1.0; P = 0.12).

Conclusion: The long-term risk of seizures was not elevated in patients with cardiac arrest who survived to hospital discharge without a seizure.

Keywords: Cardiac arrest; Epilepsy; Seizures.