Background: Vascular brain injury can result in epilepsy. It is posited that seizures in elderly patients might reflect subclinical vascular disease and thus herald future clinical vascular events.
Hypothesis: Seizures in elderly patients are associated with an increased risk of ischemic stroke or myocardial infarction (MI).
Methods: We obtained inpatient and outpatient claims data from 2008-2014 on a 5% sample of Medicare beneficiaries ≥66 years of age. The predictor variable was epilepsy, defined as two or more inpatient or outpatient claims with a diagnosis of seizure. The primary outcome was a composite of ischemic stroke or acute MI. The predictors and outcomes were all ascertained with previously validated ICD-9-CM code algorithms. Survival statistics and Cox proportional hazards models were used to assess the relationship between epilepsy and incident ischemic stroke or MI while adjusting for demographic characteristics and vascular risk factors. Patients were censored at the first occurrence of a stroke or MI, at the time of death, or on December 31, 2014.
Results: Among 1,548,556 beneficiaries with a mean follow-up of 4.4 (±1.8) years, 15,055 (1.0%) developed epilepsy and 121,866 (7.9%) experienced an ischemic stroke or acute MI. Patients with seizures were older (76.1 versus 73.7 years) and had a significantly higher burden of vascular comorbidities than the remainder of the cohort. The annual incidence of stroke or acute MI was 3.28% (95% confidence interval [CI], 3.10-3.47%) in those with seizures versus 1.79% (95% CI, 1.78-1.80%) in those without (unadjusted hazard ratio [HR], 1.89; 95% CI, 1.78-2.00). After adjustment for demographics and risk factors, epilepsy had a weak association with the composite outcome (adjusted HR, 1.36; 95% CI, 1.29-1.44), a stronger association with ischemic stroke (adjusted HR, 1.77; 95% CI, 1.65-1.90), and no association with acute MI (adjusted HR, 0.95; 95% CI, 0.86-1.04).
Conclusions: We found an association between epilepsy in elderly patients and future ischemic stroke but not acute MI. Therefore, seizures might signify occult cerebrovascular disease but not necessarily occult disease in other vascular beds.