Contribution of Adolescent Movement Behaviours to Socioeconomic Inequalities in Adult Cardiovascular Disease Risk: A Causal Decomposition in a Population-Based Cohort.

Addressing unhealthy movement behaviours in adolescence could reduce socioeconomic inequalities in adult cardiovascular disease (CVD) risk. Among 6608 adolescents enrolled in the Add Health cohort (1994-1995) and followed into adulthood (2016-2018), movement behaviours (physical activity, screen time, sleep) were classified as healthy or unhealthy based on adherence to the 24-Hour Movement Guidelines. Parental education and family financial hardship captured socioeconomic position (SEP). The outcome was 30-year CVD risk in adulthood. G-formula-based causal decomposition quantified changes in socioeconomic inequalities under two interventional scenarios: (1) eliminating unhealthy movement behaviours across the population, (2) equalizing the low-SEP group's movement behaviour distributions to match the high-SEP group. Adolescents whose parents did not graduate from college/university had a higher adult CVD risk than those whose parents did (RD: 6.9%, RR: 1.73). Eliminating all unhealthy movement behaviours reduced the RD to 4.9% (-2.0% absolute change), while the RR remained similar (1.76). Eliminating unhealthy levels of physical activity produced the largest absolute reduction (-1.7%), with negligible reductions for screen time (-0.2%) and sleep (-0.2%). The equalization scenario had minimal impact, and results were similar for family financial hardship. Whole-population interventions targeting unhealthy adolescent movement behaviours, particularly physical activity, may reduce absolute socioeconomic inequalities in adult CVD risk.