Effektmodifikation durch familiäre Prädisposition bei der Analyse des Einflusses von Stillen und Haustierhaltung auf die Entwicklung allergischer Erkrankungen bei Kindern

Abstract

Introduction: In epidemiological studies an effect modification occurs if a statistical association between an exposure and an outcome differs depending on the levels of a third variable, which is not a deficiency of the study. However, if an effect modification is not accounted for in the statistical analysis of data, this can lead to wrong conclusions and delusive interpretations of the results. Regarding the occurrence of allergic diseases in children, socio-economic status and familial predisposition are often discussed as potential effect modifiers. Methods: Using the data of a birth cohort study we demonstrate the role of familial predisposition as an effect modifier when analyzing the relationship between pet keeping as well as breastfeeding and the occurrence of allergic diseases in two years old children. A few days after delivery 3,132 mothers of German nationality were asked about education, keeping of domestic animals and family history of allergic diseases. Within the first two years of their children's life more than half of these mothers were interviewed for three more times. Important parts of these follow-up interviews were concerned with the mothers' breastfeeding behaviour as well as with symptoms of allergic diseases of the children. Results: Using stratified logistic regression models it could be shown that children living together with a dog in the same household were at higher risk of disease only if a familial predisposition of allergic diseases was present - without such a familial predisposition a dog in the same household seems to reduce the risk for atopic diseases during the first 2 years of life. A protective effect due to long breastfeeding could be observed in our study in particular in case of a paternal history of allergic diseases, whereas an exclusive maternal history of allergic diseases seems to increase the risk. Conclusion: The results of our analyses show that the influence of pet keeping and breastfeeding on the development of allergic diseases in children should only be assessed by simultaneously accounting for different patterns of family history of these diseases.