Predictors of incident epilepsy in older adults: The Cardiovascular Health Study

Abstract

Objective: To determine the prevalence, incidence, and predictors of epilepsy among older adults in the Cardiovascular Health Study (CHS).

Methods: We analyzed data prospectively collected in CHS and merged with data from outpatient Medicare administrative claims. We identified cases with epilepsy using self-report, antiepileptic medication, hospitalization discharge ICD-9 codes, and outpatient Medicare ICD-9 codes. We used Cox proportional hazards regression to identify factors independently associated with incident epilepsy.

Results: At baseline, 42% of the 5,888 participants were men and 84% were white. At enrollment, 3.7% (215 of 5,888) met the criteria for prevalent epilepsy. During 14 years of follow-up totaling 48,651 person-years, 120 participants met the criteria for incident epilepsy, yielding an incidence rate of 2.47 per 1,000 person-years. The period prevalence of epilepsy by the end of follow-up was 5.7% (335 of 5,888). Epilepsy incidence rates were significantly higher among blacks than nonblacks: 4.44 vs 2.17 per 1,000 person-years (p < 0.001). In multivariable analyses, risk of incident epilepsy was significantly higher among blacks compared to nonblacks (hazard ratio [HR] 4.04, 95% confidence interval [CI] 1.99-8.17), those 75 to 79 compared to those 65 to 69 years of age (HR 2.07, 95% CI 1.21-3.55), and those with history of stroke (HR 3.49, 95% CI 1.37-8.88).

Conclusions: Epilepsy in older adults in the United States was common. Blacks, the very old, and those with history of stroke have a higher risk of incident epilepsy. The association with race remains unexplained.

Figure 1. Risk factors for incident epilepsy with baseline comorbidities

Forest plot of adjusted hazard ratios (HRs) and 95% confidence intervals (CIs) of risk factors for incident epilepsy with comorbidities at baseline. Increased risk of incident epilepsy is to the right of the vertical axis. Table e-2 provides specific incidence rate, referent group, and p value. BMI = body mass index; CHD = coronary heart disease; CHF = congestive heart failure; CLD = claudication; IFG = impaired fasting glucose; MI = myocardial infarction; TIA = transient ischemic attack.

Figure 2. Risk factors for incident epilepsy with incident comorbidities before onset of epilepsy

Forest plot of adjusted hazard ratios (HRs) and 95% confidence intervals (CIs) of risk factors for incident epilepsy with comorbidities occurring after baseline but before onset of epilepsy (n = 87). Increased risk of incident epilepsy is to the right of the vertical axis. Table e-3 provides specific incident rates, referent group, and p values. BMI = body mass index; CHD = coronary heart disease; CHF = congestive heart failure; CLD = claudication; IFG = impaired fasting glucose; MI = myocardial infarction; TIA = transient ischemic attack.