Incidence and prevalence of treated epilepsy among poor health and low-income Americans.

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.