Objective: The International League Against Epilepsy (ILAE) has proposed to expand the definition of remission to 10 years seizure-free with the last 5years off antiepileptic drugs (AEDs). We examined if a 10-year remission is needed to predict the lowest recurrence risk.

Methods: The population-based study cohort consisted of 148 patients with new-onset childhood epilepsy living in the catchment area of Turku University Hospital. They were prospectively followed for 44years (median). Patients in first remission were prospectively followed for the duration of remission or possible relapse at 2years in remission with the last year without antiepileptic drugs (AEDs), at 5years in remission with the last 2years without AEDs, and at 10years with the last 5years without AEDs. For comparison of the proportions of relapsed patients within each remission category exact Clopper Pearson 95% confidence intervals were used.

Results: The magnitude of the relapse rate estimates off AEDs did not significantly improve when remission increased from 2 years (2YR) to 5 years (5YR) and further to 10 years (10YR). However, 10YR was a more sensitive measure of no relapse than 2YR. Among patients with remission on or off AEDs, the ability to predict lower relapse rate increased markedly from 2 to 5years, and again from 5 to 10years. The risk of relapse was virtually the same estimated after 2YR off AEDs as after 10YR on or off AEDs, except for patients with generalized epilepsy whose 2YR off AEDs was a weaker predictor than 10YR on or off AEDs.

Significance: Given the modest differences in relapse rates between the 5years seizure-free with last 2years off medications definition and the 10years seizure-free with last 5years off medications, and the adverse impact of not being considered in remission, we propose that a return to the 5-year definition may be warranted.