Abstracts

Rationale: Stroke is a common risk factor for development of epilepsy among older people. Approximately 30% of epilepsy cases in the elderly occur in people who have had a cerebrovascular event. The southeastern region of the United States has an especially high rate of stroke prevalence and has been termed the "stroke belt". We wished to examine the incidence and prevalence of epilepsy in this region. Methods: We conducted a retrospective analysis of Medicare claims for hospitalizations and outpatient visits for all Medicare beneficiaries older than 65 in the United States who had a claim with an ICD-9 code for epilepsy or seizures during the years 2001-2005. The sample was restricted to those continuously enrolled in Medicare fee-for-service at any time during these years. An epilepsy case was defined as having at least one claim with an ICD-9 code for epilepsy (345.xx) or two claims at least 30 days apart for convulsion (780.3). The 30-day criterion for the 780.3 claims was designed to exclude cases of acute symptomatic seizures which did not result in epilepsy. Incident cases were those for whom there were at least two years without a claim with these codes before the defined criteria for epilepsy. Incidence and prevalence rates were calculated for each state, and for states within the stroke belt (Alabama, Arkansas, Georgia, Louisiana, Indiana, Kentucky, Mississippi, North and South Carolina, Tennessee and Virginia) and ouside the stroke belt (all other states). Stroke belt states were as defined by the Centers for Disease Control and Prevention based on stroke mortality. Differences in rates of epilepsy between stroke belt and non-stroke belt regions were compared using two-sided chi-square tests. Results: We identified 801,076 prevalent (years 2001-2005) and 280,831 incident cases of epilepsy during these years among Medicare beneficiaries 65 years of age or older. A quarter of the prevalent cases (197, 422) and 24% of the incident cases (69, 162) were among residents of the stroke belt, but the population of the stroke belt is only 20% of the US population. The yearly incidence, and also the prevalence, of epilepsy was higher in residents of the stroke belt. Conclusions: Epilepsy was common among Medicare beneficiaries 65 years of age and older, even though we used a conservative coding definition. It is more common in the "stroke belt", probably because cerebrovascular disease is such a major cause of seizures in this age group. For older persons, there is an "epilepsy belt" corresponding to the "stroke belt". Attention to stroke prevention may reduce the incidence of epilepsy in this population. This project was supported under a cooperative agreement from the Centers for Disease Control and Prevention through the American Association of Medical Colleges, Grant#U36/CCU319276, AAMC ID#MM-1042-08/08. Publication and report contents are solely the responsibility of the authors and do not necessarily represent the official views of the AAMC or the CDC.