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Clin Exp Allergy. 1997 May;27(5):515-8.

Hay fever, asthma and number of older siblings--a twin study.

Author information

1
Department of Medicine, Helsinki University Central Hospital, Finland.

Abstract

BACKGROUND:

It has been suggested that allergic sensitization is inversely related to the number of siblings in the family.

OBJECTIVES:

To study whether a similar relation can be observed for hay fever and asthma among Finnish adolescents in a population with relatively low prevalence of atopic diseases.

METHODS:

A questionnaire mailed to a nationwide sample of 1849 families with 16-year-old twins assessing the cumulative incidence of doctor-diagnosed hay fever and asthma among the adolescents and the number of older siblings in the family by parental report.

RESULTS:

The cumulative incidence of hay fever was significantly lower among the adolescents with three or more older siblings (3.9%, 95% CI = 1.2-6.5%) compared with adolescents with fewer older siblings (12.7%, 95% CI = 11.4-14.0%). There was no difference in the cumulative incidence of asthma among the adolescents according to the number of older siblings in the family.

CONCLUSIONS:

Large number of older siblings appears to be protective against the development of hay fever.

PMID:
9179425
[Indexed for MEDLINE]

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