Higher recreational screen time and lower step count are associated with higher cardiovascular disease risk in early adolescence

Adolescence is a critical period for developing behaviors that affect lifelong cardiovascular health. While physical activity improves cardiovascular outcomes, excessive recreational screen time is linked to negative cardiovascular indicators. This study examined associations between screen time and physical activity with cardiovascular risk factors in a large, diverse sample of early adolescents. This study included 4,443 adolescents from the Adolescent Brain Cognitive Development (ABCD) Study collected at Year 2 (2018–2020) and Year 4 (2020–2022). Screen time was self-reported and categorized as low (0–4), medium (> 4–8), or high (> 8) hours/day. Physical activity was measured via Fitbit step count over 3 weeks and categorized as low (1,000–6,000), medium (> 6,000–12,000), and high (> 12,000) steps/day. Outcomes included blood pressure percentile and hypertensive-range blood pressure, which were available for the full sample, while total cholesterol, high-density lipoprotein (HDL) cholesterol, non-HDL cholesterol, hemoglobin A1c, and testing consistent with diabetes were available in a subset (one-third) at Year 4. Adjusted linear and Poisson regression models examined joint associations of screen time and step count with cardiovascular health outcomes. Adolescents averaged 6.1 (± 5.1) hours/day of screen use and 9,280 (± 3,279) steps/day. Higher screen time and lower step count showed dose-response associations with higher diastolic blood pressure percentile (all p < 0.01). Compared to reference categories, high screen time (> 8 h/day) was associated with a 4.25-point increase in diastolic blood pressure percentile (95% confidence interval [CI] 1.85 to 6.65) and low step count (1,000–6,000 steps/day) was associated with a 7.15-point increase (95% CI 4.82 to 9.48). Both high screen time (adjusted risk ratio [ARR] 1.88, 95% CI 1.42 to 2.56) and low step count (ARR 2.35, 95% CI 1.88 to 2.94) were associated with increased risk of hypertensive-range blood pressure. Low step count was associated with -3.72 mg/dL lower HDL cholesterol (95% CI -6.52 to -2.92) and increased risk of low HDL cholesterol (ARR 2.05, 95% CI 1.79 to 2.36). Higher screen time and lower physical activity were associated with poorer cardiovascular health, supporting guidelines and early interventions promoting increased physical activity and reduced screen time.