Body mass index in young children and allergic disease: gender differences in a longitudinal study

Background The increase in allergic diseases has occurred in parallel with the obesity epidemic, suggesting a possible association. Objective We investigated the relationship of body mass index (BMI) up to age 8 years with allergic disease within a birth cohort. Methods Children were followed from birth and were reviewed at age 3, 5 and 8 years (n=731; male 406). Parents completed questionnaires; children were weighed, measured, skin prick tested and examined. Results Increasing BMI at 3, 5 and 8 years increased the risk of current wheezing at the corresponding age (odds ratio [95% confidence interval] per standardized deviation score: age 3, 1.26 [1.04–1.53], P=0.02; age 5, 1.33 [1.06–1.67], P=0.02; age 8, 1.27 [1.0–1.62], P=0.05). The effect of BMI on wheeze at age 8 years differed between boys and girls, with a significant positive association in girls, but not in boys (P=0.04 for interaction). The effect of BMI at earlier ages on current or subsequent wheezing did not differ significantly between genders. Increasing BMI significantly increased the risk of physician‐diagnosed eczema at age 5 (1.23 [1.04–1.47], P=0.02) and 8 (1.23 [1.03–1.45], P=0.02), with a significant interaction between gender and BMI at age 5 (P=0.04). There was no association between BMI and sensitization. Being overweight at age 3 years was significantly associated with late‐onset wheeze (3.83 [1.51–9.75], P=0.005), persistent wheeze (4.15 [2.07–8.32], P<0.001) and persistent eczema (1.79 [1.03–3.13], P=0.04) in both boys and girls. Conclusions Being overweight is associated with an increased risk of allergic disease in childhood. However, the strength of the association varies with the gender, age and atopic phenotype. Cite this as: C. S. Murray, D. Canoy, I. Buchan, A. Woodcock, A. Simpson and A. Custovic, Clinical & Experimental Allergy, 2011 (41) 78–85.