Long-term mortality is not increased in children with febrile seizures — although there seems to be a doubling of mortality during the two years after complex febrile seizures. However, the overall risk of death associated with febrile seizures remains extremely low, and an Article in this week's edition of The Lancet concludes that parents should be reassured that death after febrile seizures is very rare, even in high-risk children.
Febrile seizure is a generalized convulsion caused by elevated body temperature. It affects 2-5% of children under 5 years old, with a third having more than one episode. Many parents think that their child is dying during the first febrile seizure and fear that they might die during subsequent seizures. While the excess mortality in children with epilepsy is well-established, mainly due to underlying neurological disorders, little is known about the mortality in children with febrile seizures. Dr Mogens Vestergaard, Department of General Practice, Institute of Public Health, Aarhus University, Denmark, and colleagues studied mortality after febrile seizures in a large cohort of children in Denmark with up to 28 years of follow up.
The study analysed 1 675 643 children born in Denmark between 1977 and 2004, each of whom was followed up from 3 months of age until death, emigration, or Aug 31 2005. The researchers identified 8172 children who died, including 232 deaths in 55 215 children with a history of febrile seizures. Overall, 132 per 100 000 children died within two years of a febrile seizure compared with 67 per 100 000 children without a history of the condition. Children who had simple febrile seizures, ie, those lasting less than 15 minutes and not recurring within 24 hours, had mortality similar to that of the general population. But in children who had had more complex febrile seizures (those lasting over 15 minutes or recurring within 24 hours) mortality was twice as high as in the general population in the two years following the seizure; thereafter, mortality returned to that seen in the general population. The authors stress that although this is a doubling of risk, the absolute risk remains small — in children followed up for two years, there would be 1 death in 1500 children in the general population, compared with 2 deaths in 1500 children who had had febrile seizures.*
The authors conclude: "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 39ºC, 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."
In an accompanying Comment, Dr Maitreyi Mazumdar, Department of Neurology, Children's Hospital, Boston, MA, USA, says: "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...[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."
*Notes to editors: the figure of 1 death per 1500 children came from dividing 100000 by 67, as this is the mortality quoted in the paper for children without a history of febrile seizures.
Dr Mogens Vestergaard, Institute of Public Health, Aarhus University, Denmark T) +45 41261133 E) mogens.vestergaard@alm.au.dk
Dr Maitreyi Mazumdar, Department of Neurology, Children's Hospital, Boston, MA, USA T) +1 617-355-2758 E)maitreyi.mazumdar@childrens.harvard.edu
http://multimedia.thelancet.com/pdf/press/febrileseizures.pdf
Journal
The Lancet