Genetic and environmental factors in epilepsy: a population-based study of11900 Danish twin pairs

The contribution of genetic and environmental factors to the occurrence of epilepsy was examined in an unselected sample of twins recruited from the p opulation-based Danish Twin Registry. Information on the occurrence of epil epsy in both members of a twin pair was obtained from 11 900 pairs whose ag es ranged From 12 to 41 years. Concordance rates, odds ratios and tetrachor ic correlations were used to quantify the similarity of monozygotic (MZ) an d dizygotic (DZ) twins. The sample was stratified by sex and separated into two age cohorts for analysis. Significantly higher probandwise concordance rates were found for MZ compared with DZ twins (0.37 and 0.08, P < 0.01). Odds ratios and tetrachoric correlation showed similar pattern. An etiologi cal model including additive genetic and individual specific environmental factors provided the best overall fit to the data, with 70 and 88% of the l iability to develop epilepsy being accounted for by genetic factors in the younger and older cohorts, respectively. Individual specific environmental factors explained the remaining 30 and 12%, respectively. In conclusion, th is study has confirmed the substantial impact, which genetic factors have i n the etiology of epilepsy. The heritability of epilepsy is high and seems to increase with age. (C) 2001 Elsevier Science B.V. All rights reserved.