Epidemiology and outcome of idiopathic generalized epilepsy in adults

Drug-resistant idiopathic generalized epilepsy (IGE) remains challenging despite a favourable overall prognosis of IGE, and little is known about basic epidemiology and long-term outcome of drug-resistant IGE. The aim of the study was to describe the incidence, prevalence and outcome of IGE in an unbiased, population-based cohort.

In 2014-2018, all patients (≥17 years) with IGE inhabiting the island of Funen (496 000 inhabitants) were recruited. The socioeconomic and clinical information available for 406 individuals was assessed. Median follow-up was 15 years.

The average IGE incidence (2008-2017) was 2.9/100 000 inhabitants/year. The point prevalence of identifiable IGE patients was 1.0/1000 adults (juvenile myoclonic epilepsy 0.4/1000; absence epilepsy 0.3/1000, epilepsy with generalized tonic-clonic seizures alone 0.3/1000); 92.1% of the patients were diagnosed before 25 years of age. When correcting for unequal age distribution in the cohort, 1102 people on the island of Funen fulfilled the diagnostic criteria for IGE at the age of 25 (estimated prevalence 2.7/1000 adults). In the year before data closure, 121 patients reported seizures. Fifty patients met the definition of drug-resistant IGE (12.1% of the cohort, 4.5% of the estimated 1102 IGE patients). The average seizure burden of all patients with drug-resistant IGE was 2.2 generalized tonic-clonic seizures per year; only 14 patients suffered more than two generalized tonic-clonic seizures per year. Drug-resistant IGE was associated with an increased risk of requiring treatment for affective disorders and a reduced probability of working full time.

Idiopathic generalized epilepsy was associated with a low risk of persistent drug-resistant seizures requiring specialist medical attention. Drug resistance was associated with a negative socioeconomic outcome.