A prospective cohort study

Long-term risk of developing epilepsy after febrile seizures

1. A. Neligan, PhD, MRCP, 
2. G.S. Bell, 
3. MD, 
4. C. Giavasi, MD, MSc, 
5. A.L. Johnson, PhD,
6. D.M. Goodridge, FRCGP, 
7. S.D. Shorvon, MD, FRCP and 
8. J.W. Sander, PhD, FRCP

+Author Affiliations

1. From the Department of Clinical and Experimental Epilepsy (A.N., G.S.B., C.G., S.D.S., J.W.S.), UCL Institute of Neurology, London, UK; MRC Biostatistics Unit (A.L.J.), Institute of Public Health, University Forvie Site, Cambridge, UK; MRC Clinical Trials Unit (A.L.J.), London, UK; Warders Medical Practice (D.M.G., former partner), Tunbridge Wells, Kent, UK; and SEIN-Epilepsy Institute in the Netherlands Foundation (J.W.S.), Heemstede, the Netherlands.

1. Correspondence & reprint requests to Prof. Sander: l.sander@ucl.ac.uk

ABSTRACT

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.