A study of asthma and allergies in 5-year-old Dutch twins

D.I. Boomsma, C.E.M. van Beijsterveldt

Dept of Biological Psychology, Vrije Universiteit, Van der Boechorstraat 1, 1081BT, Amsterdam, The Netherlands

We looked at twin resemblances for asthma and allergies in a population-based sample of 3600 young twin pairs born in The Netherlands. The parents of these twins participate in a longitudinal survey study of growth and development of their children. Around the 5th birthday of the twins, parents receive a questionnaire that contains questions about wheezing and coughing as judged by the parents in the last 12 months. Parents are also asked if a doctor ever diagnosed asthma, allergies, hayfever, eczema, bronchitis or pneumonia in their children. Results show relatively low associations between the different symptoms. For all symptoms correlations between monozygotic twins are high (0.50-0.80). In dizygotic twins the correlations are usually half the MZ correlations. There are no differences in correlations between male and female twins and the correlations in opposite-sex twins are similar to those in DZ same-sex twins. These data thus suggest: 1) strong genetic influences on the liability to asthma and allergies, 2) no sex differences in genetic architecture and 3) no influence of shared environmental factors in 5 year-old-children.