title: Childhood body mass index and wheezing disorders: a systematic review and meta-analysis.
abstract: BACKGROUND
  It has been claimed that overweight/obesity, childhood asthma and wheezing disorders are associated, although the results of observational studies have remained inconsistent. We conducted a systematic review and meta-analysis to investigate this.
  
  
  METHODS
  An online search of published papers linking childhood asthma and wheezing with overweight/obesity up to May 2014 using EMBASE and MEDLINE medical research databases was carried out. Summary odds ratios (OR) were estimated using random-effects models. Subgroup meta-analyses were performed to assess the robustness of risk associations and between-study heterogeneity.
  
  
  RESULTS
  A total of 38 studies comprising 1,411,335 participants were included in our meta-analysis. The summary ORs of underweight (<5th percentile), overweight (>85th to <95th percentile) and obesity (≥ 95 th percentile) were 0.85 (95% CI: 0.75 to 0.97; p = 0.02), 1.23 (95% CI: 1.17 to 1.29; p < 0.001) and 1.46 (95% CI: 1.36 to 1.57, p < 0.001), respectively. Heterogeneity was significant and substantial in all three weight categories, and not accounted for by pre-defined study characteristics.
  
  
  CONCLUSIONS
  Our results suggest that underweight is associated with a reduced risk of childhood asthma, and overweight and obesity are associated with an increased risk of childhood asthma. Although our findings assert that overweight/obesity and childhood asthma are associated, the causal pathway and temporal aspects of this relationship remain unanswered and deserve further epidemiological investigation.
authors.affiliation: Division of Epidemiology and Biostatistics, School of Medicine, University of Leeds, Leeds, UK.
authors.forename: Teumzghi F
authors.initials: TF
authors.lastname: Mebrahtu
authors.forename: Richard G
authors.initials: RG
authors.lastname: Feltbower
authors.forename: Darren C
authors.initials: DC
authors.lastname: Greenwood
authors.forename: Roger C
authors.initials: RC
authors.lastname: Parslow
mesh_terms: D000818:Animals; D001249:Asthma / Q000453:epidemiology*; D015992:Body Mass Index; D002648:Child; D006801:Humans; D009765:Obesity / Q000453:epidemiology*; D012135:Respiratory Sounds; D012306:Risk
keywords: ASTHMA; BMI: meta-analysis; Wheezing disorders: obesity; overweight; systematic literature review