The prevalence of epilepsy and pharmacoresistant epilepsy in adults: a population-based study in a Western European country.

Purpose: To determine the prevalence of epilepsy in a defined adult population and identify the frequency and principal features of pharmacoresistant epilepsy.

Methods: From a population over 15 years of age residing in a medium-sized French city, all patients with epilepsy on June 30, 1995 were identified from multiple sources. Pharmacoresistance was defined as failure to control epilepsy by at least two first-line antiepileptic drugs, with a seizure frequency of at least one per month for 18 months. Collected data were examined by experts in epileptology, and responding patients were reexamined using a standardized diagnostic questionnaire. ILAE definitions and classifications were used.

Results: The age-adjusted prevalence of active epilepsy was 5.4 per 1,000 (95% CI: 4.7-6.0) and was higher for males (7.8) than for females (5.2). For epilepsy in remission under treatment, this rate was 0.7 per 1,000 (95% CI: 0.5-0.95). Age-specific prevalence was highest in age groups 25-49 years and declined in the oldest age groups. Localization-related seizures represented 61.1% of cases and generalized seizures 30.9%. The proportion of noncontrolled epilepsy (seizure-frequency at least one per month for 18 months) was 15.6%, corresponding to a prevalence of 0.94 per 1,000. In this group, the mean age at onset was lower (p = 0.0007) and localization-related epilepsy more frequent (p = 0.01).

Conclusion: The findings support previous epidemiological estimates of the prevalence of epilepsy in developed countries. For approximately one patient in eight, epilepsy was not adequately controlled.