Risk of epilepsy following first unprovoked and acute seizures: Cohort study.

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First unprovoked seizures and acute seizures are common and can develop into epilepsy. The risk of epilepsy following these seizures in community samples is not well established, and it is unclear whether the probability of subsequent unprovoked seizures following these seizures reaches the International League Against Epilepsy's threshold of 60%. We followed participants initially classified as having first unprovoked seizures, having acute seizures, or without seizures in a community-based survey conducted in 2003 to estimate the subsequent risk of epilepsy in 2008 and 2021. The diagnosis of epilepsy in 2008 and 2021 was based on data from a community survey and health care visits to Kilifi County Hospital and the epilepsy clinic. Poisson regression models were used to compute incident risk ratios (IRRs) for epilepsy and population-attributable risk (PAR); population-attributable risk fractions (PAFs) were computed from contingency tables. In the 5-year follow-up (censored in 2008 survey), the IRR for epilepsy was 23.3 (95% confidence interval [CI] = 14.2-38.2) for first unprovoked seizures and 10.4 (95% CI = 5.6-19.5) for acute seizures compared to the no-seizure group. By 2021 (including 2008), the IRR was 18.4 (95% CI = 11.9-28.5) for first unprovoked seizures and 7.9 (95% CI = 4.3-14.5) for acute seizures compared to the no-seizure group. The PAR for first unprovoked seizures and acute seizures was 29.0 and 8.0/1000 persons in the long-term follow-up. The PAF was 56.3% for first unprovoked seizures and 26.3% for acute seizures in the long-term follow-up. There was a high probability that a person with acute seizures (72%) or first unprovoked seizures (92%) developed epilepsy earlier than a person from the comparison group. First unprovoked seizures and acute seizures are associated with high risk for developing epilepsy. Neurological correlates for epilepsy risk following first unprovoked seizures should be investigated to inform epilepsy diagnosis and treatment.