Association between household secondhand tobacco smoke exposure and regular e-cigarette use among adolescents: evidence from a national school-based survey.

Adolescent e-cigarette use is of public health interest in England, yet the influence of household environmental factors remains poorly understood. This cross-sectional study examined the association between secondhand tobacco smoke exposure in the home and regular e-cigarette use among adolescents. We analysed data from 12 297 adolescents aged 11-15 years who participated in the 2023 wave of the Smoking, Drinking and Drug Use among Young People in England (SDD) survey. The primary exposure was self-reported frequency of secondhand smoke exposure in the home or someone else's home, categorized into five levels. The outcome was regular e-cigarette use, defined as vaping at least once per week. Logistic regression models estimated crude and adjusted associations, controlling for age, gender identity, ethnicity, family affluence, and household or peer smoking. Regular e-cigarette use was reported by 5.8% (n = 716) of the sample. Compared to those never exposed, adolescents exposed to secondhand smoke 'daily or most days' had significantly higher odds of regular e-cigarette use [adjusted odds ratio (aOR) = 7.25; 95% confidence interval (CI): 5.62-9.34; P < .001]. A clear dose-response relationship was observed across exposure categories (P for trend <.001), with increasing exposure linked to progressively higher odds of vaping. Among adolescents who had never smoked cigarettes, daily or near‑daily exposure to household secondhand smoke was still strongly associated with regular e‑cigarette use (aOR = 5.04; 95% CI: 3.64-6.99; P < .001). Frequent secondhand tobacco smoke exposure in the home is a strong and independent correlate of regular e-cigarette use among adolescents in England.