BALTIMORE – The risk for children with febrile seizures to develop epilepsy decreased with time in an analysis of the prospective U.K. National General Practice Study of Epilepsy.

Short-term studies have shown that 1%-3% of children with febrile seizures develop afebrile seizures later in life, said Dr. Gail S. Bell of University College London Institute of Neurology.

Dr. Bell and her colleagues sought to determine if the risk of newly developing epilepsy in children with febrile seizures would decrease over time despite a continual increase in the cumulative incidence of epilepsy over time. They presented their findings in a poster at the annual meeting of the American Epilepsy Society.

They reviewed data from a cohort of 220 individuals with febrile seizures (aside from neonatal seizures) who were enrolled in the study in 1984-1987.

Overall, 68% of the children had no further seizures after their initial seizure. Of 181 individuals who were followed through 2009-2010, 175 had been free of seizures for the past 5 years, including 171 who were not taking antiepileptic drugs, the researchers noted.

However, the risk of recurrent seizures was slightly higher among children for whom the index seizure was not the first febrile seizure (hazard ratio, 1.76).

A total of 14 patients (6%) developed epilepsy and 17 (8%) developed afebrile seizures, the researchers said. Overall, "the probability of developing epilepsy by 20 years after the index seizure was 6.7%," they noted. The standardized incidence ratio for developing epilepsy was 9.7; this was highest among children aged 0-10 years with up to 10 years of follow-up, and it decreased with age until it was no longer significant in individuals aged 15-20 years with 10-20 years of follow-up.

The findings were limited by the relatively small study population, but the results suggest that epilepsy risk decreases with time in most cases, the researchers said. "Larger studies, ideally stratified by ethnic group, are required to establish whether the risk of developing epilepsy decreases to the population rate."

The study was funded by the U.K. Brain Research Trust and the U.K. Epilepsy Society. The researchers had no financial conflicts to disclose.