A Novel Methodological Approach to Measure Linear Trends in Health Inequalities: Proof-Of-Concept for Adolescent Smoking in Europe

: This paper describes a new method to present and interpret linear trends in health inequalities, and presents a proof-of-concept for inequalities in smoking among adolescents in Europe. We estimated the regression line of the assumed linear relationship between smoking prevalence in low and high socioeconomic status (SES) youth over time. Using simulation, we constructed a 95% confidence interval for the smoking prevalence in low SES youth for when this would be 0% in high SES youth, and calculated the likelihood of eradicating smoking inequality (<5% for both low and high SES). This method was applied to data of 15-16-year-olds (N=250,326) from 23 European countries, derived from the 2003-2015 ESPAD surveys. Smoking prevalence decreased more slowly in low than high SES adolescents. The estimated smoking prevalence was 9.4% (6.1;12.7) for boys and 5.4% (1.4;9.2) for girls in low SES when 0% in high SES. The likelihood of eradicating smoking inequality was <1% for boys and 37% for girls. We conclude that this novel methodological approach to trends in health inequalities is feasible in practice. Applying it to trends in smoking inequalities among adolescents in Europe, we found that Europe is currently not on track to eradicate youth smoking across SES groups.