title: Investigating the association between obesity and asthma in 6- to 8-year-old Saudi children: a matched case-control study.
abstract: BACKGROUND
  Previous studies have demonstrated an association between obesity and asthma, but there remains considerable uncertainty about whether this reflects an underlying causal relationship.
  
  
  OBJECTIVE
  To investigate the association between obesity and asthma in pre-pubertal children and to investigate the roles of airway obstruction and atopy as possible causal mechanisms.
  
  
  METHODS
  We conducted an age- and sex-matched case-control study of 1,264 6- to 8-year-old schoolchildren with and without asthma recruited from 37 randomly selected schools in Madinah, Saudi Arabia. The body mass index (BMI), waist circumference and skin fold thickness of the 632 children with asthma were compared with those of the 632 control children without asthma. Associations between obesity and asthma, adjusted for other potential risk factors, were assessed separately in boys and girls using conditional logistic regression analysis. The possible mediating roles of atopy and airway obstruction were studied by investigating the impact of incorporating data on sensitisation to common aeroallergens and measurements of lung function.
  
  
  RESULTS
  BMI was associated with asthma in boys (odds ratio (OR)=1.14, 95% confidence interval (CI), 1.08-1.20; adjusted OR=1.11, 95% CI, 1.03-1.19) and girls (OR=1.37, 95% CI, 1.26-1.50; adjusted OR=1.38, 95% CI, 1.23-1.56). Adjusting for forced expiratory volume in 1 s had a negligible impact on these associations, but these were attenuated following adjustment for allergic sensitisation, particularly in girls (girls: OR=1.25; 95% CI, 0.96-1.60; boys: OR=1.09, 95% CI, 0.99-1.19).
  
  
  CONCLUSIONS
  BMI is associated with asthma in pre-pubertal Saudi boys and girls; this effect does not appear to be mediated through respiratory obstruction, but in girls this may at least partially be mediated through increased risk of allergic sensitisation.
authors.affiliation: Allergy and Respiratory Research Group, Centre for Population Health Sciences, Medical School, The University of Edinburgh, Edinburgh, UK.
authors.forename: Mahmoud
authors.initials: M
authors.lastname: Nahhas
authors.affiliation: Bruce and John Usher Professor of Public Health, Centre for Population Health Sciences, Medical School, The University of Edinburgh, Edinburgh, UK.
authors.forename: Raj
authors.initials: R
authors.lastname: Bhopal
authors.affiliation: Allergy and Respiratory Research Group, Centre for Population Health Sciences, Medical School, The University of Edinburgh, Edinburgh, UK.
authors.forename: Chantelle
authors.initials: C
authors.lastname: Anandan
authors.affiliation: Centre for Population Health Sciences, Medical School, The University of Edinburgh, Edinburgh, UK.
authors.forename: Rob
authors.initials: R
authors.lastname: Elton
authors.affiliation: 1] Allergy and Respiratory Research Group, Centre for Population Health Sciences, Medical School, The University of Edinburgh, Edinburgh, UK [2] Division of General Internal Medicine and Primary Care, Brigham and Women's Hospital/Harvard Medical School, Boston, MA, USA.
authors.forename: Aziz
authors.initials: A
authors.lastname: Sheikh
mesh_terms: D001249:Asthma / Q000453:epidemiology / Q000209:etiology*; D015992:Body Mass Index; D016022:Case-Control Studies; D002648:Child; D005260:Female; D005541:Forced Expiratory Volume; D006801:Humans; D006967:Hypersensitivity / Q000150:complications / Q000453:epidemiology; D008297:Male; D009765:Obesity / Q000150:complications* / Q000453:epidemiology; D012307:Risk Factors; D012529:Saudi Arabia / Q000453:epidemiology; D012737:Sex Factors; D012882:Skin Tests