Objective: We report the prospective follow-up of a cohort of people from the onset of febrile seizures for a median of 24 years to estimate the long-term risk of developing epilepsy.
Methods: The National General Practice Study of Epilepsy is a large prospective community study of 1,195 people with a first suspected seizure followed from the 1980s, of whom 220 (18%) had febrile seizures. Standardized incidence ratios (SIRs) with 95% confidence intervals (CIs) for subsequent epilepsy were calculated in 5-year age bands.
Results: Follow-up information was obtained for 181 (83%) people with a mean follow-up for the whole cohort of 21.6 (SD 6.0) years. Of these, 175 (97%) were seizure-free in the preceding 5 years, whereas 171 (94%) were seizure-free and off antiepileptic drugs. Six percent developed epilepsy, but the risk of developing epilepsy in the cohort over the whole follow-up period was almost 10 times that of the general population (SIR 9.7, 95% CI 5.7-16.4). The SIR was significantly elevated in the 0- to 14-year age groups but not in the 15- to 19-year age group (SIR 4.5, 95% CI 0.6-32.1).
Conclusion: The risk of developing epilepsy in people who had febrile seizures seems to decrease with time. Further long-term studies are needed to confirm this.