Background: Evidence on respiratory symptoms due to smoking and passive smoking in children is mainly derived from studies in Western countries. Evidence from the East was required to support stronger tobacco control policy in Asia. This study aimed to analyse the relationship between respiratory symptoms and smoking status in junior secondary students and between respiratory symptoms and family smoking in never-smoking students.
Methods: In a cross-sectional survey in 1994, anonymous questionnaires were administered to a two-stage cluster probability sample of 6304 students, aged mostly 12-15 years, from 172 classes of 61 schools in Hong Kong.
Results: Significant linear trends were found between smoking and the prevalence of throat and nose problems, cough and phlegm, and wheezing. The odds ratio (OR), after adjustment for age, gender, area of residence, type of housing and correlation within schools and classes (cluster effects), for smoking at least weekly ranged from 1.35 to 4.84. In never-smoking children, significant trends were found between the number of smokers living with the children and throat and nose problems, cough and phlegm, and recent wheezing. The adjusted OR and 95% confidence interval (CI) for any cough or phlegm symptoms was 1.19 (95% CI: 1.01-1.47) for one smoking household member, 1.38 (95% CI: 1.07-1.79) for two and 1.85 (95% CI: 1.19-2.85) for three (P for trend <0.001). Increased OR were found for father and mother smoking.
Conclusions: This study provides strong evidence that both active and passive smoking can cause respiratory ill health in Chinese children in Hong Kong. Urgent measures are needed to protect children from the health hazards of active and passive smoking in Asia.