Associations between early childhood screen time and cardiometabolic risk factors in late childhood: a longitudinal study in Australia

Abstract Background Sedentary screen time in childhood has been linked to adverse health outcomes, including cardiometabolic risk factors. However, the evidence for associations remains unclear. Understanding if associations remain after adjusting for physical activity and sedentary time is important to inform early intervention strategies. This study examined screen time trajectories in early childhood and their associations with cardiovascular health outcomes, including cardiometabolic biomarkers, in late childhood. Methods We used nationally representative data from Waves 3–6 (2008–2014) of the Baby (B) cohort and the Child Health CheckPoint (2015–2016) from the Longitudinal Study of Australian Children. We used latent growth curve modelling to examine associations between trajectories of standardized screen time, measured every two years from Wave 3 (4–5 years) to Wave 6 (10–11 years), and cardiovascular health outcomes, including measures of adiposity, cardiorespiratory fitness, and blood-based cardiometabolic biomarkers, assessed at the Child Health Checkpoint (11–12 years). Secondary models were adjusted for accelerometer-derived sedentary time and moderate-to-vigorous physical activity. Results Of the 1,825 included children, 890 (49%) were female, with a mean age of 12.0 (SD = 0.4) years. Average screen time was 133 (SD = 77) minutes per day at Wave 3 (ages 4–5 years) and 196 (SD = 92) minutes per day at Wave 6 (ages 10–11 years). One standard deviation higher in model-estimated screen time at 4–5 years was associated with lower cardiorespiratory fitness ( B = -3.16, 95% CI -4.33 to -1.99), and higher waist circumference ( B = 1.18, 95% CI 0.40–1.96), waist-to-height ratio ( B = 0.01, 95% CI 0.01–0.02), BMI ( z -score; B = 0.16, 95% CI 0.06–0.26), and body fat percentage ( B = 2.01, 95% CI 1.17–2.86) at ages 11–12 years. These associations remained significant after adjusting for sedentary time and moderate-to-vigorous physical activity. No significant associations were found between screen time and blood-based cardiometabolic biomarkers after adjusting for sedentary time and moderate-to-vigorous physical activity. Conclusions Higher screen time in early childhood is associated with lower fitness and greater adiposity in late childhood, after adjusting for moderate-to-vigorous physical activity and sedentary time, but not with blood-based cardiometabolic biomarkers. These findings support limiting screen time in early childhood.