Patterns and socioeconomic differences in secondhand exposure to cigarettes, e-cigarettes, and heated tobacco products at home in Hong Kong adolescents.

Introduction: Smoke or aerosols from cigarettes, e-cigarettes (ECs), or heated tobacco products (HTPs) are harmful. Yet, there is little knowledge about the specific patterns of secondhand tobacco exposure by source within household settings and the socioeconomic status (SES) differences in adolescents.

Methods: We used territory-representative student data from a cross-sectional school-based survey in 2020-2021 to calculate the weighted prevalence of secondhand exposure to cigarettes, e-cigarettes, and HTPs in the past seven days. Parental education and perceived family affluence were used as indicators of socioeconomic status. Generalized linear mixed models were used to analyze associations.

Results: Among 22039 participants, 29.8% reported any secondhand tobacco exposure (SH-Any) at home, primarily from cigarettes (27.4%), followed by e-cigarettes (4.0%) and HTPs (0.9%). Tertiary parental education level was associated with lower SH-Any exposure (Adjusted odds ratio, AOR=0.49; 95% CI: 0.45-0.53, p<0.001), fewer exposure days (β= -0.685, p<0.001), lower exposure to cigarettes (SH-CC) (AOR=0.49; 95% CI: 0.45-0.54, p<0.001) and to e-cigarettes or HTPs (SH-EC/HTP) (AOR=0.57; 95% CI: 0.45-0.71, p<0.001). 'Poor' family affluence was associated with higher exposures [AOR(SH-Any) =1.14; 95% CI: 1.06-1.22, p=0.001; β(days)=0.160, p<0.001; AOR(SH-CC) =1.15; 95% CI: 1.07-1.24, p<0.001], except for SH-EC/HTP exposure, which was higher in students in an affluent family (AOR =1.66; 95% CI: 1.25-2.21, p<0.001). Significant SES differences in SH-EC/HTP exposure were found only in groups with low parental education level. Dose-response relationships were found between lower SH-Any and SH-CC and higher SES categories (p for trend<0.001).

Conclusions: Adolescents experienced a high prevalence of tobacco smoke exposure at home, primarily from cigarettes. Higher SES was associated with lower tobacco exposure, except for SH-EC/HTP, which was higher among adolescents from affluent families. Additionally, high parental education level was protective against exposure to SH-EC/HTP. Comprehensive control measures to reduce the use of these tobacco products are needed to protect adolescents of diverse socioeconomic backgrounds.