Effectiveness of a physical activity intervention in preschoolers: A cluster-randomized controlled trial.

Several activity interventions in preschool settings exist, but little attention has been paid to effects on hemodynamic factors. The study aimed to assess the effectiveness of an exercise program on health-related outcomes including blood pressure (BP) and markers of vascular function in preschoolers, with focus on socioeconomic background. This study is a cluster-randomized controlled trial, with preschool as unit of randomization and children as unit of analysis. Preschools with 3- to 6-year-old children, stratified by social area, were randomly allocated to: intervention (three clusters, n = 92) including 2 d·wk /45 min (6 months) exercise lessons or control (two clusters, n = 43). In total, 135 children (4.8 ± 0.8 y) had minimum one outcome measurement at baseline and follow-up. Primary outcome: peripheral BP. Secondary outcomes: central BP, pulse wave velocity (PWV), BMI, waist circumference, physical activity measures, motor skills. Maternal education was used as an indicator of socioeconomic status. Mixed models were applied to evaluate differences in mean change. Group allocation had no effect on primary or secondary outcomes. However, the intervention was effective in reducing increases in peripheral systolic BP (-3.4 mm Hg; 95% CI: -6.6; -0.2; P = 0.037), central systolic BP (-3.8 mm Hg; -6.4; -1.1; P = 0.006), and PWV (-0.1 m/s; -0.2; -0.0; P = 0.045) among children whose mothers had the lowest educational level. We found no evidence for effectiveness of a 6-months preschool-based exercise program on hemodynamics, anthropometrics, activity, or motor skills, but lack of process evaluations and poor fidelity preclude interpretation of the causal relation. However, the results indicate that children from lower social backgrounds could benefit from early exercise-promoting interventions.