title: Body mass index in young children and allergic disease: gender differences in a longitudinal study.
abstract: 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.
authors: Manchester Academic Health Science Centre, NIHR Translational Research Facility in Respiratory Medicine, University Hospital of South Manchester NHS Foundation Trust, The University of Manchester, Manchester, UK. clare.murray@manchester.ac.uk
authors: C S
authors: CS
authors: Murray
authors: D
authors: D
authors: Canoy
authors: I
authors: I
authors: Buchan
authors: A
authors: A
authors: Woodcock
authors: A
authors: A
authors: Simpson
authors: A
authors: A
authors: Custovic
mesh_terms: D000367:Age Factors; D001249:Asthma / Q000175:diagnosis; D015992:Body Mass Index; D002648:Child; D002675:Child, Preschool; D015331:Cohort Studies; D004485:Eczema / Q000175:diagnosis; D005260:Female; D006801:Humans; D006967:Hypersensitivity / Q000175:diagnosis / Q000503:physiopathology*; D007231:Infant, Newborn; D008137:Longitudinal Studies; D008297:Male; D011446:Prospective Studies; D012307:Risk Factors; D012727:Sex Characteristics