While there is a lot of research on the ‘age of the first occurrence’ it is much more difficult to find research on the recurrences of febrile seizures in general. Unfortunately though, it is reported that febrile seizures recur in about 30% of cases. According to our own Seizure Report results, 36% of reported seizures are seizure #2 or greater.
Furthermore, recurrent febrile seizures do not necessarily occur at the same temperature as the first episode, and do not occur every time the child has a fever. Research has shown that 50% of the recurrent seizures occur in the first 2 hours after onset of a subsequent fever episode and that if the seizure recurs at a later time, the temperature at seizure is higher compared with recurrences occurring in the first 2 hours of fever.
The risk of recurrent febrile seizures is higher for children who:
- Are young (less than 18 months)
- Have a parent or sibling who had febrile seizures or epilepsy
- Have a short time between the onset of fever and the seizure
- Had a low degree of fever before their seizure
Specifically research has shown that the recurrence risk for those with none of these 4 risk factors was only 4%, with 1 factor it rose to 23%, with 2 factors 32%, with 3 factors 62%, and with all 4 factors 76%.
Research is inconclusive on whether a longer initial febrile seizure (i.e. a complex seizure or status epilepticus) affects the risk of recurrent febrile seizures, however, recent research suggests that an iron deficiency may be a risk factor for febrile seizures.
And finally, most recurrences occur within one year of the initial seizure and almost all occur within two years. That is the risk of a recurrent febrile seizure reduces year-on-year as discussed on the When will my child grow out of it page.