Estimating causal effects of physical activity and sedentary behaviours on the development of type 2 diabetes in at-risk children from childhood to late adolescence: an analysis of the QUALITY cohort

Background.Uncertainty remains regarding the causal effect of physical activity and sedentary behaviors on type 2 diabetes (T2D) development in children.The objective of our study was to estimate average treatment effects (ATEs) of physical activity and sedentary behaviors on T2D risk in childhood and adolescence.Methods.We used data from the QUebec Adipose and Lifestyle InvesTigation in Youth (QUALITY) cohort of children with a parental history of obesity evaluated at 8-10 years (n=630), 10-12 years (n=564) and 15-17 years (n=377), in Québec, Canada (2005-2015).We measured moderate-to-vigorous physical activity (MVPA) and sedentary time by accelerometry, and leisure screen time by questionnaire at each cycle.Outcomes included fasting and 2-h glycemia and validated indices of insulin sensitivity and insulin secretion.We estimated ATEs of MVPA, sedentary time, and screen time on markers of T2D using longitudinal marginal structural models with time-varying exposures, outcomes and confounders from 8-10 to 15-17 years and inverse probability of treatment and censoring weighting.We considered both the current and cumulative effects of exposures on outcomes.Findings.Based on cumulative exposure results, estimated ATEs for MVPA were 5•6% (95% CI: 2•8; 8•5) on insulin sensitivity and -3•8% (-7•1; -0•5) on second-phase insulin secretion per 10minute daily increment across 8-10 to 15-17 years.ATEs for sedentary time and reported screen time yielded reduced insulin sensitivity (-8•2% [-12•3; -3•9] and -6•4% [-10•1; -2•5], respectively), increased second-phase insulin secretion (5•9% [1•9; 10•1] and 7•0% [-0•1; 14•7], respectively), and higher fasting glycemia (0•03 mmol/L [0•003; 0•05] and 0•02 mmol/L [0•01; 0•03], respectively) per supplemental daily hour from 8-10 to 15-17 years.