• Epilepsy;
  • Seizures;
  • Incidence;
  • Health maintenance organizations;
  • Epidemiology

Summary: 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.

Methods: 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 (0.73–1.49) 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.