Changes in prevalence and socioeconomic inequalities in secondhand smoke exposure in Spanish children, 2016-2019.

Introduction: Children are vulnerable to secondhand smoke (SHS) exposure, especially those with lower socioeconomic status. This study assesses the changes in prevalence and socioeconomic inequalities in SHS exposure in children younger than 12 years old in Spain between 2016 and 2019.

Methods: We conducted two cross-sectional studies among representative samples of households with children aged <12 years in Spain, in 2016 (n=2411) and 2019 (n=2412). Families were interviewed to assess children's SHS exposure in private settings and outdoor public venues and their adoption of home and car smoke-free rules. We used the education level of the home main earner as a proxy for socioeconomic position. Changes over time in the prevalence and socioeconomic inequalities of SHS exposure and smoke-free rules were estimated through adjusted Poisson regression models with robust variance according to sociodemographic covariates (adjusted prevalence ratios, APRs).

Results: In 2019, 70.5% of children were exposed to SHS in Spain. No changes between 2016 and 2019 were found for overall SHS exposure, exposure at home, and at school entrances. SHS exposure increased at public transport stations (APR=1.24; 95% CI: 1.03-1.49) and outdoor hospitality venues (APR=1.17; 95% CI: 1.07-1.29) while it decreased in cars (APR=0.74; 95% CI: 0.56-0.98) and parks (APR=0.87; 95% CI: 0.77-0.98). Households with lower education level had higher prevalence of SHS exposure at home in 2019 compared with those with university studies (primary: APR=1.30; 95% CI: 1.11-1.51; secondary: APR=1.12; 95% CI: 1.00-1.25) and were less likely to adopt home indoor smoke-free rules (primary: APR=0.88; 95% CI: 0.79-0.99; secondary: APR=0.95; 95% CI: 0.89-1.02). Socioeconomic inequalities in SHS exposure at home persisted between 2016 and 2019 (p>0.05), while decreased in smoke-free rules in cars (p=0.039).

Conclusions: Reported SHS exposure among children in Spain remained high between 2016 and 2019. Inequalities persisted at home, highlighting the need for measures to reduce such exposure with an equity perspective.