Social Inequalities in Secondhand Smoke Among Japanese Non-smokers: A Cross-Sectional Study

Yusuke Matsuyama, Jun Aida, Toru Tsuboya, Shihoko Koyama, Yukihiro Sato, Atsushi Hozawa, Ken Osaka

Secondhand smoke (SHS) causes many deaths. Inequalities in SHS have been reported in several countries; however, the evidence in Asian countries is scarce. We aimed to investigate the association between socioeconomic status (SES) and SHS at home and the workplace/school among non-smoking Japanese adults. Cross-sectional data from the Miyagi Prefectural Health Survey 2014 were analyzed. Self-reported questionnaires were randomly distributed to residents ≥20 years of age and 2,443 (92.8%) responded. The data of the 1,738 and 1,003 respondents were included to the analyses for SHS in the past month at home and at the workplace/school, respectively. Ordered logistic regression models considering possible confounders, including knowledge of the adverse health effects of tobacco, were applied. The prevalence of SHS at home and the workplace/school was 19.0% and 39.0%, respectively. Compared with ≥13 years of education, odds ratios (ORs) and 95% confidence intervals (CIs) for SHS at home were 1.94 (95% CI, 1.42-2.64) for 10-12 years and 3.00 (95% CI, 1.95-4.60) for ≤9 years; those for SHS at the workplace/school were 1.80 (95% CI, 1.36-2.39) and 3.82 (95% CI, 2.29-6.36), respectively. Knowledge of the adverse health effects of tobacco was significantly associated with lower SHS at home (OR 0.95; 95% CI, 0.91-0.98) but it was not associated with SHS at the workplace/school (OR 1.02; 95% CI, 0.98-1.06). Social inequalities in SHS existed among Japanese non-smoking adults. Knowledge about tobacco was negatively associated with SHS at home but not at workplace/school.