Subgroup differences in the associations between dog exposure during the first year of life and early life allergic outcomes

Background The effect of dog exposure on the risk of children developing allergic disease remains controversial. Many analyses have not considered that associations may vary within population subgroups. Objective Examine whether associations between living with a dog in the first year of life and allergic outcomes vary within subgroups selected a priori (race, gender and delivery mode). Methods Black (n=496) and White (n=196) children enrolled in the WHEALS birth cohort study had a clinical examination at age 2 years to assess eczema and allergen-specific IgE (sIgE) and perform skin prick testing (SPT). Whether the child lived with an indoor dog in the first year of life was assessed through interview, as was doctor diagnosis of asthma at ages 3-6 years. Results Living with a dog was associated with decreased odds of having ≥1 positive SPT (OR=0.56, 95%CI 0.34, 0.91) and having eczema (OR=0.34, 95%CI 0.20, 0.60). The association with SPT was stronger in those children born via cesarian-section versus vaginally (OR=0.29, 95%CI 0.12, 0.74 versus OR=0.76, 95%CI 0.43, 1.37, respectively, interaction p=0.087) and in those who were firstborn versus not (OR=0.27, 95%CI 0.11, 0.67 versus OR=0.82, 95%CI 0.45, 1.47, respectively, interaction p=0.044). The association with eczema was stronger in children born vaginally compared with those born via cesarian-section (OR=0.17, 95%CI 0.06, 0.43 versus OR=0.65, 95%CI 0.31, 1.35, respectively, interaction p=0.025) and was stronger in Black versus White children (OR=0.30, 95%CI 0.15, 0.61 versus OR=0.78, 95%CI 0.29, 2.11, respectively, interaction p=0.12). Dog keeping was not significantly inversely associated with having ≥1 elevated sIgE and only approached statistical significance with asthma. This article is protected by copyright. All rights reserved.