Siblings, multiple births, and the incidence of allergic disease: a birth cohort study using the West Midlands general practice research database
- 1 October 2001
- Vol. 56 (10), 758-762
- https://doi.org/10.1136/thorax.56.10.758
Abstract
BACKGROUND The presence of older siblings reduces the risk of developing hay fever, eczema and atopy, but findings for asthma have been inconsistent. Whether twins have a reduced risk of allergic disease is also unclear. We have investigated these questions in a birth cohort analysis of the West Midlands General Practice Research Database (GPRD). METHODS Our birth cohort included 29 238 children. The incidence of allergic disease was examined according to the number of siblings, multiple births, and parental allergic disease and smoking habit using Cox regression. RESULTS There was a dose related decrease in the incidence of eczema and hay fever with increasing number of older siblings (hazard ratio for children with three or more older siblings compared with none 0.70 (95% CI 0.64 to 0.76) for eczema and 0.67 (95% CI 0.52 to 0.86) for hay fever). In contrast, the presence of older siblings increased the incidence of asthma (HR 1.17, 95% CI 1.06 to 1.29), although this effect was strongly dependent on age of diagnosis. For children diagnosed over the age of 2 years the presence of older siblings was protective (HR 0.66, 95% CI 0.52 to 0.82), while below this age the reverse was true (HR 1.38, 95% CI 1.24 to 1.54). Members of a multiple birth had a reduced incidence of all three allergic diseases. Birth order and multiple birth effects were independent of sex, maternal age, consulting behaviour, and parental allergy and smoking habit. CONCLUSIONS The presence of older siblings and being a member of a multiple birth appears to protect against the development of eczema, hay fever, and asthma diagnosed after the age of 2. In contrast, the presence of older siblings increases the incidence of early asthma.Keywords
This publication has 16 references indexed in Scilit:
- Reduced risk of hospital admission for childhood asthma among Scottish twins: record linkage studyBMJ, 2000
- Association between asthma and family size between 1977 and 1994Journal of Epidemiology and Community Health, 1999
- Cross sectional study of the relation between sibling number and asthma, hay fever, and eczemaArchives of Disease in Childhood, 1998
- Perinatal risk factors for atopic disease in conscriptsClinical and Experimental Allergy, 1998
- Family size, childhood infections and atopic diseases. The Aberdeen WHEASE GroupThorax, 1998
- Family size, atopic disorders in parents, asthma in children, and ethnicityJournal of Allergy and Clinical Immunology, 1997
- Study of the aetiology of wheezing illness at age 16 in two national British birth cohorts.Thorax, 1996
- Prospective study of risk factors for early and persistent wheezing in childhoodEuropean Respiratory Journal, 1995
- Asthma and Wheezing in the First Six Years of LifeNew England Journal of Medicine, 1995
- Hay fever, hygiene, and household size.BMJ, 1989