title: A systematic review of the relationship between asthma, overweight, and the effects of physical activity in youth.
abstract: The association of asthma and overweight in youth is well studied. However, the temporal relationship between asthma and overweight, the strength of their association, and mediating factors involved in this relationship remain unclear. This review investigates the relationship between asthma and overweight in youth, while examining the role of physical activity as a mediator.
  
  
  
  A systematic review of literature was conducted using PubMed and Medline databases. Studies conducted among youth aged 0-18 years, published in English between 2000-2014 were included. The Strengthening the Reporting of Observational Studies in Epidemiology guidelines were consulted to evaluate quality of selected citations.
  
  
  
  A comprehensive search yielded 143 studies in PubMed and 133 studies in Medline databases. Of these, 75 studies met the eligibility criteria. The review found varying hypotheses regarding the temporal relationship between asthma and overweight in youth; existing evidence supports the mediation of this association by decreased expenditure of energy due to reduced physical activity. Negative self-perception or parental perception of exercise ability due to asthma symptoms secondary to physical exertion was identified as a determinant of physical activity in asthmatic youth.
  
  
  
  Physical activity likely mediates the relationship between asthma and overweight in youth. Temporality of this relationship remains unclear.
authors.affiliation: Department of Biostatistics and Epidemiology, College of Public Health, East Tennessee State University, Johnson City.
authors.forename: Edward
authors.initials: E
authors.lastname: Leinaar
authors.affiliation: Department of Biostatistics and Epidemiology, College of Public Health, East Tennessee State University, Johnson City. Electronic address: alamian@etsu.edu.
authors.forename: Arsham
authors.initials: A
authors.lastname: Alamian
authors.affiliation: Department of Biostatistics and Epidemiology, College of Public Health, East Tennessee State University, Johnson City.
authors.forename: Liang
authors.initials: L
authors.lastname: Wang
mesh_terms: D000293:Adolescent; D001249:Asthma / Q000453:epidemiology* / Q000503:physiopathology; D015992:Body Mass Index; D016022:Case-Control Studies; D015897:Comorbidity; D015444:Exercise; D005260:Female; D006801:Humans; D015994:Incidence; D008019:Life Style; D008137:Longitudinal Studies; D008297:Male; D050177:Overweight / Q000453:epidemiology* / Q000503:physiopathology; D063766:Pediatric Obesity / Q000453:epidemiology* / Q000503:physiopathology; D018570:Risk Assessment; D017678:Sex Distribution; D014481:United States / Q000453:epidemiology
keywords: Adolescent; Asthma; Child; Exercise; Obesity; Review