Abstracts

The incidence of seizures peaks in childhood and declines in adolescence with febrile seizures (FS) being the most common type of seizure in childhood and a well established risk factor for epilepsy. While the results of numerous studies have demonstrated the importance of the contribution of genetic factors to risk for epilepsy, these studies have, for the most part, not focused on epilepsy in children and adolescents. This study was undertaken to examine the epidemology of FS and epilepsy in young Danish twins and estimate the relative contribution of genetic factors to their risk of occurrence. Mailed questionnaires were used to obtain information pertinent to history of FS and epilepsy in twins included in 15.000 pairs born between 1983 and 2001. This sample was extracted from the population-based Danish Twin Registry. Point prevalences and odds ratios (OR) were estimated for FS and epilepsy in this sample. Probandwise concordance rates were used to assess the contribution of genetic factors to seizure/epilespy risk. Among 19778 twins where information on seizure history was available, 996 and 162 reported FS and epilepsy, respectively; and 41 twins reported to have both FS and epilepsy. The point prevalences of seizures in this sample were 5% (FS), 0.82% (epilepsy) and 0.21% for FS and epilepsy. For an estimated FS prevalence of 3%, the OR was 1,71 (95% CI = 1,54-1,90). At an estimated prevalence of 5%, the OR decreased to 1,01 (95% CI = 0,92-1,10). The OR for epilepsy at an estimated prevalence of 0.84% was 0.98 (95% CI = 0.79-1.21). Probandwise concordance rates for FS in this sample were 0.544 (MZ) and 0.170 (DZ). For epilepsy, the probandwise concordance rate for MZ twins was 0.348 and 0.097 for DZ twins. For the group reporting both FS and epilepsy, probandwise concordance rates were 0.5 and 0.174 for MZ and DZ tiwns, respectively. The point prevalence of FS found in this sample is quite similar to that estimated in Western Europe and the US; while the point prevalence of epilepsy is very similar to that seen in the UK for subjects aged 0-23. The OR observed indicate that twins do not have an increased risk for either FS or epilepsy. The results obtained further indicate that genetic factors play an important role in the development of FS and epilepsy in childhood and adolescence. (Supported in part by the following grants: National Institutes of Health NINDS grant (NS 31564); The grant committee of Consultancy Counsel, Odense University Hospital; The Lennart Gram Memorial Foundation; The Jakob Madsen and wife Olga Madsen Foundation.)