FAMILY-SIZE, ATOPIC DISORDERS IN PARENTS, ASTHMA IN CHILDREN, AND ETHNICITY

Background: Several studies have reported an association between famil y size and atopic conditions, but few have found an association betwee n asthma and family size. Objective: This study was designed to assess the effect of familial aggregation and sibling number on asthma in ch ildren. Methods: Children from 5 to 11 years of age in England and Sco tland participated in a study in 1990 or 1991 in which responses to qu estions on asthma and wheezing in children and atopic conditions in pa rents were ascertained. Data on 11,924 complete family sets of child, mother, and father in three samples (the ''representative'' samples of England and Scotland and the English ''inner city'' sample) were anal yzed. Results: The following factors were highly associated with child 's asthma or wheezing: mother's or father's asthma or wheezing (with t he same odds ratio [OR], 2.4; 95% confidence interval [CI], 2.0 to 2.9 ), other atopic condition in mothers and fathers (OR, 1.5; 95% CI, 1.3 to 1.8 and OR, 1.4; 93% CI, 1.2 to 1.7, respectively), and three or m ore siblings compared with no siblings (OR, 0.5; 95% CI, 0.4 to 0.6). Conclusion: The negative relation between family size and wheezing or asthma indicates a protective effect of number of children sharing an environment at a younp age, The level of association of asthma or whee zing in the parents and the child and the association between the chil d's asthma or wheezing and other atopic conditions in parents suggest that a general susceptibility and a lung-specific susceptibility are i mportant in the etiology of asthma.