Association between exposure to secondhand aerosol from heated tobacco products and respiratory symptoms among current non-smokers in Japan: a cross-sectional study

OBJECTIVES: To investigate the association between secondhand-aerosol exposure from heated tobacco products (HTPs) and respiratory symptoms among current non-smokers. DESIGN: Cross-sectional study. SETTING: Internet survey conducted between 8 and 26 February 2021 in Japan. PARTICIPANTS: Non-smoking respondents at the survey aged 15–80 years. EXPOSURE: Self-reported secondhand-aerosol exposure. PRIMARY AND SECONDARY OUTCOMES: We defined asthma/asthma-like symptoms as a primary outcome and persistent cough as a secondary outcome. We examined the association between secondhand-aerosol exposure from HTPs and respiratory symptoms (asthma attacks/asthma-like symptoms and persistent cough). The prevalence ratio (PR) and 95% CI were calculated by using weighted, multivariable ‘modified’ Poisson regression models. RESULTS: Of the 18 839 current non-smokers, 9.8% (95% CI 8.2% to 11.7%) and 16.7% (95% CI 14.8% to 18.9%) of those who were exposed to secondhand aerosols reported asthma attacks/asthma-like symptoms and persistent cough, whereas 4.5% (95% CI 3.9% to 5.2%) and 9.6% (95% CI 8.4% to 11.0%) of those who were not, respectively. Secondhand-aerosol exposure was associated with respiratory symptoms (asthma attacks/asthma-like symptoms: PR 1.49, 95% CI 1.21 to 1.85; persistent cough: PR 1.44, 95% CI 1.21 to 1.72) after adjusting for covariates. CONCLUSION: Secondhand-aerosol exposure from HTPs was associated with both asthma attacks/asthma-like symptoms and persistent cough. These results provide policymakers with meaningful information in the regulation of HTP use for the protection of current non-smokers.