title: Risk factors for non-atopic asthma/wheeze in children and adolescents: a systematic review.
abstract: BACKGROUND
  The study of non-atopic asthma/wheeze in children separately from atopic asthma is relatively recent. Studies have focused on single risk factors and had inconsistent findings.
  
  
  OBJECTIVE
  To review evidence on factors associated with non-atopic asthma/wheeze in children and adolescents.
  
  
  METHODS
  A review of studies of risk factors for non-atopic asthma/wheeze which had a non-asthmatic comparison group, and assessed atopy by skin-prick test or allergen-specific IgE.
  
  
  RESULTS
  Studies of non-atopic asthma/wheeze used a wide diversity of definitions of asthma/wheeze, comparison groups and methods to assess atopy. Among 30 risk factors evaluated in the 43 studies only 3 (family history of asthma/rhinitis/eczema, dampness/mold in the household, and lower respiratory tract infections in childhood) showed consistent associations with non-atopic asthma/wheeze. No or limited period of breastfeeding was less consistently associated with non-atopic asthma/wheeze. The few studies examining the effects of overweight/obesity and psychological/social factors showed consistent associations. We used a novel graphical presentation of different risk factors for non-atopic asthma/wheeze, allowing a more complete perception of the complex pattern of effects.
  
  
  CONCLUSIONS
  More research using standardized methodology is needed on the causes of non-atopic asthma.
authors: Universidade Federal da Bahia, Instituto de Saude Coletiva, Rua Basilio da Gama s/n, 40110-040 Salvador, Bahia, Brazil.
authors: Agostino
authors: A
authors: Strina
authors: Universidade Federal da Bahia, Instituto de Saude Coletiva, Rua Basilio da Gama s/n, 40110-040 Salvador, Bahia, Brazil.
authors: Mauricio L
authors: ML
authors: Barreto
authors: St George's University of London, Division of Clinical Sciences, Cranmer Terrace, London SW17 ORE, UK.
authors: Philip J
authors: PJ
authors: Cooper
authors: London School of Hygiene & Tropical Medicine, Faculty of Epidemiology and Population Health, Keppel Street, London WC1E 7HT, UK.
authors: Laura C
authors: LC
authors: Rodrigues
keywords: Mould; Non-atopic asthma; Non-atopic wheeze; Respiratory infections; Risk factors