title: Childhood asthma and physical activity: a systematic review with meta-analysis and Graphic Appraisal Tool for Epidemiology assessment.
abstract: BACKGROUND
  Childhood asthma is a global problem affecting the respiratory health of children. Physical activity (PA) plays a role in the relationship between asthma and respiratory health. We hypothesized that a low level of PA would be associated with asthma in children and adolescents. The objectives of our study were to (1) summarize the evidence available on associations between PA and asthma prevalence in children and adolescents and (2) assess the role of PA in new-onset or incident asthma among children and adolescents.
  
  
  METHODS
  We searched Medline, the Cochrane Library, and Embase and extracted data from original articles that met the inclusion criteria. Summary odds ratios (ORs) and confidence intervals (CIs) were used to express the results of the meta-analysis (forest plot). We explored heterogeneity using funnel plots and the Graphic Appraisal Tool for Epidemiology (GATE).
  
  
  RESULTS
  We retrieved 1,571 titles and selected 11 articles describing three cohort and eight cross-sectional studies for inclusion. A meta-analysis of the cohort studies revealed a risk of new-onset asthma in children with low PA (OR [95 % CI] 1.32 [0.95; 1.84] [random effects] and 1.35 [1.13; 1.62] [fixed effects]). Three cross-sectional studies identified significant positive associations between childhood asthma or asthma symptoms and low PA.
  
  
  CONCLUSIONS
  Children and adolescents with low PA levels had an increased risk of new-onset asthma, and some had a higher risk of current asthma/or wheezing; however, there was some heterogeneity among the studies. This review reveals a critical need for future longitudinal assessments of low PA, its mechanisms, and its implications for incident asthma in children. The systematic review was prospectively registered at PROSPERO (registration number: CRD42014013761; available at: http://www.crd.york.ac.uk/PROSPERO [accessed: 24 March 2016]).
authors.affiliation: Department of Odontology, University of Copenhagen, Copenhagen, 1014, Denmark. rkb664@alumni.ku.dk.
authors.forename: Lene
authors.identifier: http://orcid.org/0000-0003-4955-1869
authors.initials: L
authors.lastname: Lochte
authors.affiliation: Department of Pediatrics and Adolescent Medicine, Copenhagen University Hospital, Rigshospitalet, Copenhagen, 2100, Denmark.
authors.forename: Kim G
authors.initials: KG
authors.lastname: Nielsen
authors.affiliation: Department of Odontology, University of Copenhagen, Copenhagen, 1014, Denmark.
authors.forename: Poul Erik
authors.initials: PE
authors.lastname: Petersen
authors.affiliation: Department of Medicine, Division of Allergy and Clinical Immunology, University of Virginia, Charlottesville, 22908, VA, USA.
authors.forename: Thomas A E
authors.initials: TA
authors.lastname: Platts-Mills
mesh_terms: D000293:Adolescent; D001249:Asthma / Q000453:epidemiology / Q000209:etiology* / Q000517:prevention & control; D002648:Child; D002675:Child, Preschool; D014943:Global Health; D006801:Humans; D015994:Incidence; D007223:Infant; D007231:Infant, Newborn; D015233:Models, Statistical; D009043:Motor Activity; D015995:Prevalence; D065840:Protective Factors; D012307:Risk Factors
keywords: Asthmatic disease; Exercise; Pediatric; Systematic review