Sibship size, birth order, and atopy in 11,371 Italian young men,☆☆,,★★

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Abstract

Background: Having a low number of siblings and a low birth order has been reported to be a relevant risk factor for development of atopic diseases and skin sensitization to common inhalants. Although the inverse association of atopy with sibship size has been confirmed repeatedly, the association with birth order has provided conflicting results. This possibly is due to the relatively small size of the population sample examined. Objective: The objective of this study was to investigate the relation between sibship size, birth order, and atopy in a very large population sample, highly homogeneous for age and sex. Methods: This was a retrospective survey of 11,371 Italian young men, 18 to 24 years old, all candidates for enrollment in the Italian Air Force. Demographic data had been collected by a standard questionnaire. Specific IgE for locally relevant airborne allergens had been tested by a multi-RAST assay (CAP-Phadiatop). Results: The prevalence of atopy (defined as a high level of specific IgE against inhalants [cut-point >1.2 log RU]) was inversely related to the total number of siblings (25% in those with no siblings and 9% in those with five or more siblings), with a mean of a 3% decrease in prevalence for each added sibling. This relation persisted after adjustment for relevant variables such as father's education and rural and southern residence. An independent association between birth order and atopy was also observed because the decrease in atopy prevalence with increasing numbers of older siblings was significantly steeper than that found with the number of younger siblings (X2 = 179, df = 1, p < 0.0001). Conclusions: In a very large and homogeneous population sample of a Mediterranean country, not only sibship size but also birth order was significantly associated with atopy. This observation further highlights the role of family structure in the development of atopy and supports the hypothesis that cross-infections acquired early in infancy or in later childhood might prevent development of atopy later in life. (J Allergy Clin Immunol 1998;101:439–44.)

Section snippets

Population sample

Data collected from a population of 11,371 Italian young men (19.7 ± 1.49 years old) were used for the current study. These subjects were candidates to be enrolled in the Italian Air Force (IAF) as permanent professionals and were examined by the medical departments of the IAF in Vigna di Valle (Rome) and in Capodichino Air Force Base (Naples) in the period from 1991 to 1996. These centers carry out several recruitment sessions each year. Data collection was built around existing examination

Sibship size and atopy

The frequency distribution curves of the overall serum concentration of IgE antibody against common airborne allergens according to the number of siblings at the time of testing are reported in Fig. 1.

. Percentage frequency distribution of overall degree of serum IgE sensitization to common airborne allergens in 11,371 Italian young men according to sibship size. Peak prevalence in high-positivity area (log RU >1.2) can be observed in the group of “only-child” subjects. This peak progressively

DISCUSSION

We found a strong inverse relation between sibship size and serum IgE sensitization toward common airborne allergens in a very large population sample of Italian young men. Studies performed in the British3, 16 and German6 populations already examined the influence of family structure on atopic diseases. In these studies, however, atopy was defined by self-reported hay fever,3 eczema, 16 or respiratory allergy 9 or by in vivo testing for skin sensitization.6, 7 Our data provide the in vitro

Acknowledgements

We are most grateful to David P. Strachan for his advice on the statistical test for difference between the effects of older and younger siblings on atopy and to Michele Fortini, Roberto Vitalone, Angelo Di Pietro, Marco Rampolli, and Antonio Rossi for excellent technical assistance.

References (22)

  • D Jarvis et al.

    The association of family size with atopy and atopic disease

    Clin Exp Allergy

    (1997)
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    From aLab. di Immunologia ed Allergologia, Divisione Aerea Studi Ricerche e Sperimentazioni, Pomezia (Rome); bIstituto Medico Legale A.M. “Aldo di Loreto,” Napoli; and cIstituto Superiore di Sanità, Laboratorio di Epidemiologia e Biostatistica, Rome.

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    Supported by IAF 3001-94/96.

    Reprint requests: Paolo M. Matricardi, MD, DASRS, Lab. di Immunologia ed Allergologia, Aeroporto Pratica di Mare, 00040 Pomezia (Rome), Italy.

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