Risk factors for febrile convulsions.
BACKGROUND
Little is known about the relative importance of genes and early environment in the etiology of febrile convulsions.


METHODS
We performed a follow-up study using data from two nationwide registers in Denmark, 1980-1998. The study population comprised 10,224 younger siblings of children who had had febrile convulsions, and 21,218 younger siblings of children who had never been hospitalized with febrile convulsions.


RESULTS
The study provides three main findings. First, if a previous child had had a febrile convulsion, the risk was lower for the next child if either parent changed partners. Compared with full-siblings, the hazard ratio (HR) of febrile convulsions was 0.6 for paternal half-siblings and 0.7 for maternal half-siblings. In contrast, if there was no history of febrile convulsions in the previous child, a change in partner was associated with a slight increase in risk (1.2 among paternal half-siblings and 1.3 among maternal half-siblings). Secondly, the risk of febrile convulsion was strongly associated with the number of hospitalizations for febrile convulsions experienced by the older siblings, with a doubling of risk among those whose older sibling had had three or more hospitalizations. Thirdly, the risk of febrile convulsions increased with decreasing gestational age, birth weight, and birth weight ratio regardless of family history.


CONCLUSIONS
Our data suggest that the etiology of febrile convulsions depends on a genetic susceptibility that can be transmitted through both parents, and corroborates the hypothesis that multiple febrile convulsions may constitute a separate etiological entity.
Vestergaard
Mogens
M
Perinatal Epidemiological Research Unit, Department of Obstetrics and Gynaecology, Aarhus University Hospital, Skejby, DK-8200 Aarhus N, Denmark. mv@dadlnet.dk
Basso
Olga
O
Henriksen
Tine Brink
TB
Østergaard
John R
JR
Olsen
Jørn
J
D001724:Birth Weight; D002675:Child, Preschool; D003718:Denmark / Q000453:epidemiology; D005260:Female; D005500:Follow-Up Studies; D020022:Genetic Predisposition to Disease; D005865:Gestational Age; D006801:Humans; D007223:Infant; D008297:Male; D009679:Nuclear Family; D016016:Proportional Hazards Models; D003294:Seizures, Febrile / Q000453:epidemiology* / Q000235:genetics*