Household secondhand tobacco exposure in adolescents : trends, socioeconomic differences and smokefree home restrictions

Abstract

Secondhand smoke (SHS) exposure at home in adolescents is prevalent and disproportionately high in those with low socioeconomic status (SES). Creating a smokefree home (SFH) could reduce SHS exposure at home but is challenging to implement. Additionally, adopting SFH restrictions is associated with reduced cigarette susceptibility, but the underlying pathways are unknown. This thesis aims to investigate (1) long-term changes in household SHS exposure and related socioeconomic differences; (2) patterns and socioeconomic differences in secondhand exposure to cigarettes, e-cigarettes (ECs) and heated tobacco products (HTPs); (3) practices, facilitators and barriers to achieving a SFH; and (4) the association between SFH restrictions and tobacco susceptibility, including the mediating roles of tobacco attitudes and peer tobacco use.

Quantitative data were from School-based Smoking Surveys among Students from 2010 to 2020. Qualitative data were from 28 in-depth interviews with parent tobacco users living with children aged ≤14 years on their SFH practices and perceptions. Mixed-effects regression models were used to investigate the temporal trend of household SHS exposure from 2010 to 2020, patterns and socioeconomic differences in exposure to different products, and the association between SFH restrictions and tobacco susceptibility. Thematic analysis was used to investigate SFH practices, facilitators and barriers among parental tobacco users. Structural equation models were used to explore mediating effects.

From 2010 to 2020, SHS exposure inside the home increased by 26.8% (from 23.5% to 29.8%), and exposure from neighbours increased by 142.3% (from 16.8% to 40.7%). Overall, household SHS exposure from any source increased from 33.2% to 58.5%. Adolescents with lower parental education levels and from poor families were more likely to be exposed, with widening disparities, especially by parental education since 2018.

Cigarettes (27.4%) were the major source of tobacco exposure at home, followed by ECs (4.0%) and HTPs (0.9%). While tertiary parental education was negatively associated with exposure to any products, rich family affluence was associated with EC/HTP exposure (adjusted odds ratio=1.66).

Parents had varied knowledge of SHS risks and SFH practices, often partially enforced or with violations. Barriers to creating a SFH included low awareness of thirdhand smoke and EC exposure, nicotine dependence, stress, unsuitable weather, and inadequate home environments and smokefree legislation.

In 2016,25.2% of adolescents who never used tobacco were living in smoking households, but only 43.3% of them were protected by SFH restrictions with strict adherence. Having strict SFH restrictions was associated with lower susceptibility to cigarette or EC use, and this relationship was mediated by less tolerant attitudes toward tobacco.

In conclusion, household secondhand tobacco exposure is increasing in Hong Kong adolescents, with widening SES disparities. High parental education serves as a protective factor against any exposure. Understanding culturally specific facilitators and barriers to creating a SFH could inform further intervention programs. Setting strict SFH restrictions may positively influence adolescents by fostering negative tobacco attitudes, potentially reducing their susceptibility to tobacco use and offering promise for future prevention efforts. Continuous monitoring and targeted interventions are needed to address increasing household tobacco exposure, related SES disparities, and encourage the creation of SFHs.