The emergence of socioeconomic inequalities in smoking over the life-course

Abstract

Background Despite the notable progress in tobacco control, tobacco is still an important problem worldwide. Furthermore, most studies report a strong association between education and smoking: less educated men are more likely to smoke; and there is also a gradient of smoking for women, although less marked than for men. This is a serious public health problem since is known that educational inequalities in smoking contribute substantially to the existence of inequalities in mortality. The educational differences in smoking are already observed in early life. Smoking is more common among those adolescents whose parents have lower educational levels and, particularly, in adolescents with lower own educational levels. However, there is still some uncertainty regarding the time inequalities emerge, and what explains their trends. This study aimed to find whether and how educational inequalities in smoking evolve from pre-adolescence until young adulthood. The present study tested these results in the Portuguese context, and for differences between men and women. Methods This study used data from the EPITeen Cohort that recruited 13-year-old adolescents born in 1990 and enrolled at public and private schools of Porto, Portugal. The participants were followed across four waves: 2003–2004, 2007/2008, 2011/2013, and 2014/2015. For this analysis, we considered 1038 participants. We evaluated the smoking status at each wave, and classified the participants as never smokers, experimenters, less than daily smokers, daily smokers, former experimenters (the ones that experimented in the past, but stopped and never smoked again), and former smokers. We modelled whether the smoking behaviours were influenced by the future educational attainment, since we hypothesized that education inequalities might emerge early, before adolescents complete their education (for example due to educational aspirations or expectations about the future). We computed the odds ratio of the logistic regressions for prevalence and incidence of smoking, adjusted by life stage (survey year) and participant's achieved education, and also with interactions for life stage with participant's achieved education. We then estimated the prevalence and incidence of smoking, using generalized estimating equation models. We stratified both the analyses by sex. Results The results showed that men with lower academical achievement were more likely to experiment until 17-years-old (OR = 1.72 for high education, and OR = 0.38 for the interaction with 17-years-old). However, those with higher academical achievement were more likely to experiment later, between 17- and 21-years-old (OR for the interaction was 0.72). Less of participants with higher academical achievement became daily smokers: despite the prevalence of daily smoking being very low at 13-years-old, the inequalities arose already at 17-years-old (OR for high education was 0.65, and for the interaction with 17 years and education was 0.49), and they were increasing with age. Former experimenters and former smokers prevalence were higher among low educated men, yet the differences were very small, and decreasing with age. Among women, the inequalities followed the same trends observed among men, except for inequalities in former experimenting, which were more prevalent among low educated, but reversed between 21- and 24-years-old. Conclusion Inequalities were formed in a cumulative way across the life-course: the inequalities in daily smoking were formed between 13- and 17-years-old with inequalities in smoking experimentation, and between 17- and 21-years-old with inequalities in daily smoking. Late adolescence and early adulthood were already important to define inequalities. Since the inequalities emerged early in life, and persisted after that, policies should already pay special attention to 13–21-year-old-group.