Persistence of parental‐reported asthma at early ages: A longitudinal twin study

BACKGROUND: Currently, we cannot predict whether a pre‐school child with asthma‐like symptoms will have asthma at school age. Whether genetic information can help in this prediction depends on the role of genetic factors in persistence of pre‐school to school‐age asthma. We examined to what extent genetic and environmental factors contribute to persistence of asthma‐like symptoms at ages 3 to asthma at age 7 using a bivariate genetic model for longitudinal twin data. METHODS: We performed a cohort study in monozygotic and dizygotic twins from the Netherlands Twin Register (NTR, n = 21,541 twin pairs). Bivariate genetic models were fitted to longitudinal data on asthma‐like symptoms reported by parents at age 3 and 7 years to estimate the contribution of genetic and environmental factors. RESULTS: Bivariate genetic modeling showed a correlation on the liability scale between asthma‐like symptoms at age 3 and asthma at age 7 of 0.746 and the contribution of genetics was estimated to be 0.917. The genetic analyses indicated a substantial influence of genetic factors on asthma‐like symptoms at ages 3 and 7 (heritability 80% and 90%, respectively); hence, contribution of environmental factors was low. Persistence was explained by a high (rg = 0.807) genetic correlation. CONCLUSION: Parental‐reported asthma‐like symptoms at age 3 and asthma at age 7 are highly heritably. The phenotype of asthma‐like symptoms at age 3 and 7 was highly correlated and mainly due to heritable factors, indicating high persistence of asthma development over ages 3 and 7.