Considering the age-graded nature of associations between socioeconomic characteristics and smoking during the transition towards adulthood.

Young adulthood is a sensitive period characterized by the accumulation of resources and transitions in and out of education, employment, family, and housing arrangements. The association between these characteristics and smoking outcomes likely varies with age yet few studies address its dynamic age-graded nature. To explore this, we examined 2083 young adults ages 18-25 from the 2011-2012 cross-sectional sample of the Montreal-based Interdisciplinary Study of Inequalities in Smoking. We operationalized participants' socioeconomic characteristics using their resources (e.g., education, income, financial difficulties) and transition stages (i.e., studying, working full-time, living arrangements with parents and children, and being in a relationship). We examined differences in these characteristics' associations with occasional and daily smoking across two-year categories (18-19, 20-21, 22-23, and 24-25) using multinomial logistic regression models with age-based interaction terms. Findings highlighted four characteristics, i.e., educational attainment, personal income, student status, and relationship status, with significant differences in associations with smoking outcomes across age categories. Between the age groups of 18-19 and 24-25: 1) the negative association between low educational attainment and daily smoking increased; 2) the positive association between personal income and daily smoking decreased; 3) the negative association between student status and both outcomes decreased; 4) the negative association between relationship status and occasional smoking increased. Findings support that the associations between young adults' socioeconomic characteristics and smoking outcomes vary substantially during the second and third decades of life. Addressing this has critical implications for identifying vulnerable populations and developing appropriate age-based policies in this age group.