Abstracts

Rationale: Estimates of the incidence and prevalence of epilepsy in the U.S. are largely based upon data from many years ago and have not represented the U.S. population as a whole. Given the need for more current epidemiologic data to inform the care of people with epilepsy, we sought to determine the prevalence and incidence of epilepsy within 2 health insurance claims databases representing large sectors of the US population. Methods: This was a retrospective observational analysis using Commercial Claims and Medicare Supplemental (CC&M) and Medicaid insurance claims data between January 1, 2007 and December 31, 2011. Over 20 million continuously enrolled lives of all ages were included. Our definition of a prevalent case of epilepsy was based on ICD-9-CM coded diagnoses of epilepsy or seizures and evidence of prescribed antiepileptic drugs. Incident cases were identified among prevalent cases who were continuously enrolled for ≥2 years before the year of incidence determination with no epilepsy or seizure diagnoses or antiepileptic drug prescriptions recorded. Results: During 2010 and 2011, the overall age-adjusted prevalence estimate, combining weighted estimates from all data sets, was 8.4 cases of epilepsy per 1,000 population. Examining CC&M and Medicaid data separately, the age-adjusted prevalence estimates were 5.0 and 34.3 per 1,000, respectively, for the same period. The overall age-adjusted incidence estimate for 2011, combining weighted estimates from data sets, was 79.1 per 100,000 population. The combined weighted age-specific estimates of epilepsy incidence found a substantially higher rates in persons <5 or >60 years of age. Comparing age-specific incidence from CC&M and Medicaid data revealed far higher rates among Medicaid enrollees 20 to 64 years of age. Conclusions: Using large administrative data sources and the methods described, we have derived a weighted, age-adjusted estimate of epilepsy prevalence that is within the range of other estimates published from developed countries. The derived combined weighted age-adjusted estimate of annual epilepsy incidence is distinctly higher than the median estimate obtained by an evidence-based review of population-based incidence studies. The combined weighted age-specific estimates of epilepsy incidence show a distribution similar to those of many other studies. Study Funded By UCB Inc.