A new study reviewed in The Lancet reports that the overall risk of death associated with febrile seizures is extremely low. Research conducted by Dr. Mogens Vestergaard, and colleagues, at the Department of General Practice, Institute of Public Health, Aarhus University, Denmark, found that death following a simple febrile seizure is very rare. However, they also did find that the risk of death appears to double in the 2 years that follow a complex febrile seizure.

Simple febrile seizures last less than 15 minutes and do not recur within 24 hours; complex seizures last more than 15 minutes and / or recur within 24 hours. Children who had more complex seizures had a mortality rate twice as high as the general population in the 2 years following the seizures, but children with simple seizures had mortality rates similar to those of the general population.

Because little is known about the effect of febrile seizures on mortality in children, the Danish researchers studied 675,643 children born in Denmark between 1977 and 2004, analyzing mortality after febrile seizures and following them up to 28 years post-seizure: from 3 months old until they died, emigrated, or until August 31, 2005.

Of the original sample, 8,172 eventually died, which included 232 of the 55,215 children with a history of febrile seizure. Researchers found that 132 per 100,000 children died within the 2 year period following a febrile seizure. Sixty-seven per 100,000 died without having a history of the condition.

The authors note that, in spite of the increased risk associated with complex seizures, the absolute risk remains small.

The authors conclude that "Children with simple febrile seizures had a risk of death similar to the background population, whereas those with complex febrile seizures, febrile seizures triggered by temperature below 39°C, and febrile seizures occurring before 12 months of age had a two-fold higher mortality lasting for about two years. The excess mortality was at least partly due to pre-existing neurological abnormalities and subsequent epilepsy…Parents should be reassured that death after febrile seizures is very rare, even in high-risk children."

Further, Dr. Maitreyi Mazumdar of the Department of Neurology, Children's Hospital, Boston, states that "Vestergaard and colleagues' study again seems to refute, for infants and children who have simple febrile seizures, the idea of a shared cause between febrile seizures and sudden death.”

Mazumdar adds that the study “suggests that there is a subset of children with febrile seizures - notably those with complex features and underlying neurological abnormalities - that may warrant closer attention and follow-up."