Objectives: To determine the incidence and prevalence of treated epilepsy in an adult Medicaid population.Methods: We performed a retrospective, dynamic cohort analysis using Ohio Medicaid claims data between 1992 and 2006. Individuals aged 18-64 years were identified as prevalent cases if they had $2 claims of epilepsy (ICD-9-CM: 345.xx) or $3 claims of convulsion (ICD-9-CM: 780.3 or 780.39) and $2 claims of antiepileptic drugs. Incident cases were required to have no epilepsy or convulsion claims for $5 years before epilepsy diagnosis. Subjects were determined as having preexisting disability and/or comorbid conditions, including brain tumor, depression, developmental disorders, migraine, schizophrenia, stroke, and traumatic brain injury, when at least one of these conditions occurred before epilepsy onset.Results: There were 9,056 prevalent cases of treated epilepsy in 1992-2006 and 1,608 incident cases in 1997-2006. The prevalence was 13.2/1,000 (95% confidence interval, 13.0-13.5/ 1,000). The incidence was 362/100,000 person-years (95% confidence interval, 344-379/ 100,000 person-years). The incidence and prevalence were significantly higher in men, in older people, in blacks, and in people with preexisting disability and/or comorbid conditions. The most common preexisting conditions in epilepsy subjects were depression, developmental disorders, and stroke, whereas people with brain tumor, traumatic brain injury, and stroke had the higher risk of developing epilepsy.
Conclusions:The Medicaid population has a high incidence and prevalence of epilepsy, in an order of magnitude greater than that reported in the US general population. This indigent population carries a disproportionate amount of the epilepsy burden and deserves more attention for its health care needs and support services. Medicaid, financed jointly by the US federal and state governments, provides health care coverage for low-income families and for individuals with disabilities. Medicaid is the single largest health insurer in the United States with an average monthly enrollment of nearly 60 million beneficiaries.1 In general, subjects enrolled in Medicaid are educationally and socioeconomically disadvantaged and a large number of them have disabling physical and/or mental ailments, several of which are also risk factors for epilepsy. However, no study, to our knowledge, has specifically examined the incidence and/or prevalence of epilepsy in this subgroup of the US population. Both incidence and prevalence data on Medicaid beneficiaries are crucial for the complete understanding of the burden of epilepsy in the United States. Moreover, this information is necessary for planning appropriate actions or interventions to provide needed health care and support services for this highly vulnerable subgroup of the population. This study was designed to estimate the incidence and prevalence of epilepsy in the Medicaid population. We