title: February asthma outbreaks in NSW: a case control study.
abstract: OBJECTIVE
  To investigate individual factors associated with an asthma outbreak among children aged one to 14 years in Sydney in February 1999.
  
  
  METHODS
  A case control study was undertaken with cases (n=92) defined as all children admitted to Sydney Children's Hospital for asthma in February 1999. Unmatched controls (n=76) were all children admitted for asthma in the previous three months. We obtained information by a structured telephone survey of parents. Logistic regression analyses were used to determine odds ratios for risk factors for hospital admission.
  
  
  RESULTS
  Mean age for hospital admission of 4.7 years for cases and 4.4 years for controls. The presence of one or more siblings reduced the risk of admission during an asthma outbreak (OR=0.59, 95% CI 0.37 to 0.93). Children with older siblings aged 10 to 14 years were also less likely to be admitted (OR=0.3, 95% CI 0.12 to 0.74). An age effect was observed. Other demographic, clinical and environmental characteristics, including smoking, were not associated with admission during the outbreak.
  
  
  CONCLUSIONS
  The main findings of this study are the protective effect of siblings and an age-dependent effect in risk of hospital admission during an asthma outbreak. These findings are consistent with an infective cause of the outbreak.
  
  
  CONCLUSIONS
  Children without siblings, particularly older siblings, appear to be at highest risk of hospital admission during an asthma outbreak. Environmental and other factors need to be examined to further explain the episodicity of such outbreaks and to determine means of predicting and preventing future episodes.
authors.affiliation: Environmental Health Branch, New South Wales Health Department, Gladesville.
authors.forename: S
authors.initials: S
authors.lastname: Lister
authors.forename: V
authors.initials: V
authors.lastname: Sheppeard
authors.forename: G
authors.initials: G
authors.lastname: Morgan
authors.forename: S
authors.initials: S
authors.lastname: Corbett
authors.forename: J
authors.initials: J
authors.lastname: Kaldor
authors.forename: R
authors.initials: R
authors.lastname: Henry
mesh_terms: D000293:Adolescent; D018927:Anti-Asthmatic Agents / Q000627:therapeutic use; D001249:Asthma / Q000188:drug therapy / Q000453:epidemiology* / Q000503:physiopathology; D016022:Case-Control Studies; D002648:Child; D002675:Child, Preschool; D004196:Disease Outbreaks; D006776:Hospitals, Pediatric / Q000706:statistics & numerical data; D006801:Humans; D007223:Infant; D016015:Logistic Models; D009517:New South Wales / Q000453:epidemiology; D009679:Nuclear Family; D010343:Patient Admission / Q000706:statistics & numerical data*; D012307:Risk Factors
chemical_list: D018927:Anti-Asthmatic Agents