Epidemiology of absence epilepsy. I. Concept and incidence.

An epidemiological study of absence epilepsy is presented. The study comprised a series of cases from a Swedish population, aged 0-15 years, selected on the basis of EEG criteria. All children with regular and symmetrical 3 (2-4) Hz spike-and-slow-wave complexes, recorded for the first time during the period 1978-1982, were included. A total of 134 children fulfilled the inclusion criteria, and of these, 108 (80.6%) had absences alone or in combination with general tonic-clonic seizures (GTCS); 11 (8.2%) had absences combined with other seizures; 15 (11.2%) had other types of seizures only. The mean annual incidence of absence epilepsy was 7/100,000 for children aged 0-15 years. Of these, 6.3/100,000 had absences alone or in combination with GTCS. The cumulative incidence of absence epilepsy was 98/100,000. The mean age of onset was 7 years.