Causal decomposition to evaluate movement behaviour changes on cardiovascular health inequalities

Abstract Background Individuals of lower socioeconomic position (SEP) are at increased risk of developing cardiovascular disease (CVD). Variability in movement behaviours, including physical activity, sedentary behaviour, and sleep, contributes to CVD risk and socioeconomic gradients in cardiovascular health. Movement behaviour habits often begin early in life, with adolescence representing a sensitive period for establishing behaviour patterns that persist into adulthood. This study aims to evaluate the extent to which socioeconomic inequalities in adult CVD risk can be mitigated by using causal decomposition to model interventional scenarios on unhealthy movement behaviours during adolescence. Methods We will conduct a population-based cohort study of adolescents from the Add Health study, recruited in 1994-1995 from the United States and followed into adulthood. Unhealthy movement behaviours - low moderate-to-vigorous physical activity, high recreational screen time, and short sleep duration - will be operationalized based on the 24-hour Movement Guidelines and measured twice during adolescence (12-24 years). Parental education and family financial hardship will be used to measure SEP. The outcome will be the 10-year risk of CVD, as measured in adulthood (33-41 years) using a validated risk score. G-formula-based causal decomposition with time-varying covariates will be used to quantify the change of socioeconomic inequalities in adult CVD risk under two interventional scenarios: (1) elimination (unhealthy movement behaviours are eliminated in the population during adolescence) and, (2) equalization (the distributions of unhealthy movement behaviours in the low SEP group during adolescence are equalized to those in the high SEP group). Conclusions This study will use causal decomposition methods to estimate policy-relevant effects, providing evidence to guide interventions targeting adolescent movement behaviours and reduce socioeconomic inequalities in CVD risk.