title: Heritability and shared genetic effects of asthma and hay fever: an Italian study of young twins.
abstract: A number of studies have provided evidence of a significant familial aggregation for both asthma and hay fever, and have reported a substantial comorbidity between the two conditions. However, far fewer, especially in Italy, have aimed at clarifying the origins of such comorbidity. The main aims of the present study were (a) to estimate heritability of asthma and hay fever, (b) to measure the association between asthma and hay fever at the individual level, and (c) to assess the extent to which genetic and environmental factors, shared by the two conditions, mediate this association. The twin method was used. The study sample was derived from the Italian Twin Registry, and included 392 twin pairs aged 8 to 17 years. Data collection was performed through parent self-administered questionnaire. Bivariate structural equation twin modeling was applied to asthma and hay fever. Genetic factors accounted for 92% and 78% of the variance in liability to asthma and hay fever, respectively, with the remaining contributions due to unique environmental influences. The within-individual association between asthma and hay fever was substantial. The genetic correlation between the two conditions was .58, whereas no evidence of overlapping unique environmental effects was found. In conclusion, this study showed a high heritability of asthma and hay fever in the Italian child and adolescent population. It also indicated that asthma and hay fever share, to a large extent, a common genetic background, and environmental factors are not relevant to explain the comorbidity.
authors: National Centre for Epidemiology, Surveillance and Health Promotion, Istituto Superiore di Sanità, Rome, Italy. corrado.fagnani@iss.it
authors: Corrado
authors: C
authors: Fagnani
authors: Isabella
authors: I
authors: Annesi-Maesano
authors: Sonia
authors: S
authors: Brescianini
authors: Cristina
authors: C
authors: D'Ippolito
authors: Emanuela
authors: E
authors: Medda
authors: Lorenza
authors: L
authors: Nisticò
authors: Valeria
authors: V
authors: Patriarca
authors: Daniela
authors: D
authors: Rotondi
authors: Virgilia
authors: V
authors: Toccaceli
authors: Maria Antonietta
authors: MA
authors: Stazi
mesh_terms: D000293:Adolescent; D001249:Asthma / Q000453:epidemiology / Q000235:genetics*; D016009:Chi-Square Distribution; D002648:Child; D004200:Diseases in Twins / Q000453:epidemiology / Q000235:genetics*; D005260:Female; D006801:Humans; D007558:Italy / Q000453:epidemiology; D008297:Male; D008957:Models, Genetic; D016017:Odds Ratio; D015995:Prevalence; D006255:Rhinitis, Allergic, Seasonal / Q000453:epidemiology / Q000235:genetics*; D012307:Risk Factors