title: Exposure to secondhand smoke from neighbours and respiratory symptoms in never-smoking adolescents in Hong Kong: a cross-sectional study.
abstract: OBJECTIVE
  To investigate secondhand smoke (SHS) exposure at home from neighbours in Hong Kong adolescents and its association with respiratory symptoms in never-smokers.
  
  
  METHODS
  A cross-sectional study.
  
  
  METHODS
  79 randomly selected secondary schools in Hong Kong.
  
  
  METHODS
  61,810 secondary 1 (USA grade 7) to 7 students, in which 50,762 never-smokers were identified and included in the analysis of the association between SHS exposure at home from neighbours and respiratory symptoms.
  
  
  METHODS
  Smoking status, family smoking status, SHS exposure at home from inside the home and from neighbours in the past 7 days, respiratory symptoms and sociodemographic characteristics were reported. Adjusted ORs (AORs) of respiratory symptoms for SHS exposure from the 2 sources in never-smokers were calculated using logistic regression.
  
  
  RESULTS
  In all students, 33.2% were exposed to SHS at home, including 16.2% from inside the home only, 10.0% from neighbours only and 7.0% from both. The prevalence of SHS exposure from neighbours was 17.1%, including 13.5% for 1-4 days/week and 3.6% for 5-7 days/week. In never-smokers (n=50,762), respiratory symptoms were significantly associated with SHS exposure from neighbours with AORs (95% CI) of 1.29 (1.20 to 1.39) for any exposure (p<0.001), 1.21 (1.12 to 1.31) for 1-4 days/week (p<0.001) and 1.63 (1.44 to 1.86) for 5-7 days/week (p<0.001) (P for trend <0.001). Compared with no SHS exposure at home from any source, the AORs were 1.16 (1.07 to 1.25) for SHS from inside the home only (p<0.001), 1.20 (1.11 to 1.31) from neighbours only (p<0.001), and 1.74 (1.56 to 1.94) from both (p<0.001).
  
  
  CONCLUSIONS
  SHS exposure at home from neighbours was prevalent in Hong Kong adolescents, and was associated with respiratory symptoms in never-smokers. SHS exposure at home may be underestimated by ignoring the neighbouring source. Smoke-free housing policy is needed to protect children and adolescents from harms of SHS.
authors.affiliation: School of Public Health, The University of Hong Kong, Hong Kong.
authors.forename: Lok Tung
authors.initials: LT
authors.lastname: Leung
authors.affiliation: School of Public Health, The University of Hong Kong, Hong Kong.
authors.forename: Sai Yin
authors.initials: SY
authors.lastname: Ho
authors.affiliation: School of Nursing, The University of Hong Kong, Hong Kong.
authors.forename: Man Ping
authors.initials: MP
authors.lastname: Wang
authors.affiliation: School of Public Health, The University of Hong Kong, Hong Kong.
authors.forename: Wing Sze
authors.initials: WS
authors.lastname: Lo
authors.affiliation: School of Public Health, The University of Hong Kong, Hong Kong.
authors.forename: Tai Hing
authors.initials: TH
authors.lastname: Lam
mesh_terms: D000293:Adolescent; D002648:Child; D003430:Cross-Sectional Studies; D005260:Female; D006723:Hong Kong / Q000453:epidemiology; D006801:Humans; D016015:Logistic Models; D008297:Male; D012120:Respiration Disorders / Q000453:epidemiology* / Q000209:etiology*; D012574:Schools; D057566:Self Report; D014028:Tobacco Smoke Pollution / Q000706:statistics & numerical data*
chemical_list: D014028:Tobacco Smoke Pollution
keywords: Multi-unit housing; Respiratory symptoms; Secondhand smoke