The incidence of epilepsy and unprovoked seizures in multiethnic, urban health maintenance organizations

Purpose: Studies of the incidence of epilepsy are limited to a few populations in which new cases can be ascertained. Health maintenance organization (HmO) populations were studied to determine the incidence in a multiethnic, urban United States population. Method's: Cases of initial unprovoked seizure disorder or epilepsy while enrolled in an HMO between 1988 and 1994 were ascertained. Ethnicity was obtained from the medical records and was part of a nested case-control study. Results: There were 197 incidence cases of epilepsy and 275 of initial unprovoked seizure diagnosis. The incidence rate in the age range 0-64 years was 35.5 per 100,000 for epilepsy and 50.9 for initial unprovoked seizure. When compared with population-based studies, rates were slightly higher in children younger than 15, similar for the 15- to 24-year age group, but lower for ages 25-64 years. The ethnicity-specific odds ratios for initial unprovoked seizure, by using non-Hispanic white as the referent,were 1.04 (0.73-1.39) for African-American, 0.97 (0.64-1.48) for Hispanic, and 0.25 (0.08-0.84) for Asian-American. Conclusions: The lower rate in the HMO population is presumably due to a healthy-worker effect. The ethnicity-specific incidence rates do not differ in this population.