Frequency-risk relationships between second-hand smoke exposure and respiratory symptoms among adolescents: a cross-sectional study in South China

Objectives

Although previous studies have suggested an association between second-hand smoke (SHS) exposure and respiratory symptoms, current evidence is inconsistent. Additionally, it remains unclear whether there are frequency–risk relationships between SHS exposure and respiratory symptoms among adolescents.

Methods

A cross-sectional survey was conducted using a stratified cluster sampling method to obtain a representative sample of high school students in Guangzhou, China. The respiratory symptoms were defined as persistent cough or sputum for three consecutive months during the past 12 months. Self-reported SHS exposure was defined as non-smokers' inhalation of the smoke exhaled from smokers on ≥1 day a week in the past 7 days. The univariable and multivariable logistic regression models were fitted to explore the potential frequency–risk relationships between SHS exposure and respiratory symptoms.

Results

Among 3575 students, the overall prevalence of SHS exposure was 69.2%, including 49.5% for SHS in public places, 34.5% in homes, 22.7% in indoor campuses and 29.2% in outdoor campuses. There were significantly increased risks of having respiratory symptoms corresponding to SHS exposure in public places (OR=1.60, 95% CI 1.30 to 1.95), in homes (OR=1.53, 95% CI 1.25 to 1.87), in indoor campuses (OR=1.43, 95% CI 1.14 to 1.79) and in outdoor campuses (OR=1.37, 95% CI 1.10 to 1.69) using no exposure as reference. Notably, we observed monotonic frequency–risk relationships between setting-specific(eg, homes, public places and campuses) SHS exposure and respiratory symptoms.

Conclusion

Our findings suggest that setting-specific SHS exposure is associated with a significant, dose-dependent increase in risk of respiratory symptoms.

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