title: Cow's milk exposure and asthma in a newborn cohort: repeated ascertainment indicates reverse causation.
abstract: The effect of cow's milk consumption on childhood asthma has been debated for several years. This study attempts to provide further insight into this association through the use of a longitudinal study design. Newborns from parents with atopic history were recruited from Germany, Austria, and England (n = 696). For five repeated ascertainments, information was collected on cow's milk exposure, incidence of doctor-diagnosed asthma, and confounders. Generalized estimation equations, incorporating different models (concurrent, delayed, combined, and reverse causation), were used to determine this association. No association between cow's milk consumption and childhood asthma was found for the concurrent effects model (OR = 0.81, 95% confidence interval [CI]: 0.55, 1.20). In the delayed effects model, the direction of the association varied with time of follow-up. Thus, we stratified by period, which resulted in a significant protective delayed effect at 36 months (OR = 0.18, 95% CI = 0.06, 0.49). However, reverse causation negated this finding since the presence of asthma in prior months led to a reduction in further exposure to cow's milk (OR = 0.40, 95% CI = 0.16, 0.99). Hence, cow's milk consumption does not protect against childhood asthma. The apparent protection of cow's milk against asthma may result from parents of asthmatic children avoiding cow's milk, rather than actual prophylaxis.
authors: Michigan State University, College of Human Medicine, Department of Epidemiology, East Lansing, Michigan, USA.
authors: Chris
authors: C
authors: Fussman
authors: David
authors: D
authors: Todem
authors: Johannes
authors: J
authors: Forster
authors: Hassan
authors: H
authors: Arshad
authors: Radvan
authors: R
authors: Urbanek
authors: Wilfried
authors: W
authors: Karmaus
mesh_terms: D000818:Animals; D001249:Asthma / Q000453:epidemiology / Q000276:immunology*; D002417:Cattle; D015331:Cohort Studies; D005060:Europe / Q000453:epidemiology; D005260:Female; D006801:Humans; D007231:Infant, Newborn; D016015:Logistic Models; D008137:Longitudinal Studies; D008297:Male; D008892:Milk / Q000009:adverse effects / Q000276:immunology*; D016269:Milk Hypersensitivity / Q000276:immunology