title: Eczema, birth order, and infection.
abstract: The association between infections occurring in the first 2 years of life and development of eczema was investigated in 1,782 control children from a national population-based case-control study in the United Kingdom conducted over the period 1991-1996. Dates of eczema and infectious diagnoses were ascertained from contemporaneously collected primary care records. Children diagnosed with eczema before the age of 2 years had more prior clinically diagnosed infections recorded than did children without eczema (rate ratio = 1.26, 95% confidence interval (CI): 1.18, 1.36). The difference in infection rates between children with and without eczema was apparent from birth and throughout the first 2 years of life. As expected, compared with children of second or higher birth order, those firstborn were at increased risk of eczema (p = 0.020); however, the relation between eczema and prior infection was evident only among children of second or higher birth order and not among firstborn children (rate ratio = 1.45, 95% CI: 1.32, 1.59, and rate ratio = 1.08, 95% CI: 0.98, 1.20, respectively). The authors' results are consistent with the notion that the association between birth order and eczema is unlikely to be attributable to variations in early infectious exposure.
authors.affiliation: Epidemiology and Genetics Unit, Department of Health Sciences, University of York, Heslington, York, United Kingdom.
authors.forename: Ann Maree
authors.initials: AM
authors.lastname: Hughes
authors.forename: Simon
authors.initials: S
authors.lastname: Crouch
authors.forename: Tracy
authors.initials: T
authors.lastname: Lightfoot
authors.forename: Pat
authors.initials: P
authors.lastname: Ansell
authors.forename: Jill
authors.initials: J
authors.lastname: Simpson
authors.forename: Eve
authors.initials: E
authors.lastname: Roman
mesh_terms: D001722:Birth Order; D016022:Case-Control Studies; D004485:Eczema / Q000453:epidemiology / Q000209:etiology*; D005260:Female; D006801:Humans; D015994:Incidence; D007223:Infant; D007239:Infections / Q000150:complications*; D016015:Logistic Models; D008297:Male; D016012:Poisson Distribution