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Dose-Response Relationship in a Healthy Habits Study for Head Start Preschoolers.

BACKGROUND
Understanding the dose-response relationship in behavioral interventions is critical to guide future research efforts. However, only few studies have fully examined the dose-response relationship especially among children.


OBJECTIVE
To examine the relationships between level of participation and intervention effects.


METHODS
The study used data from 39 Head Start parent-preschooler dyads participating in a 10-week lifestyle intervention. The intervention included daily center-based preschooler program, preschooler weekly letters to parents, parent meetings, and weekly Facebook-based program. Height, weight, waist circumference (WC), moderate-to-vigorous physical activity (MVPA), screen time, and fruit/vegetable intake were assessed.


RESULTS
Preschooler program average daily attendance was 79%, and Facebook-based program average completion rate was 80%. About 49% attended all three parent meetings. Parent meeting attendance was significantly and positively related to preschoolers' vegetable intake (p = .023), MVPA (p < .001), and parents' MVPA (p = .016). Preschooler letters were significantly and negatively related to preschoolers' screen time (p = .002) and parents' WC (p = .027), and positively correlated with parents' MVPA (p = .01). Preschooler program attendance was not significantly correlated with their BMI (ρ = -.31) or WC (ρ = -.16).The study provides important information for designing effective interventions among low-income families. The findings imply that (1) parent-only interventions and parent-child interventions may result in similar effects, (2) future behavioral interventions should focus on the bidirectional parent-child relationship, and (3) it is important to include face-to-face contacts in lifestyle interventions. In addition, it highlights the need to examine the dose-response relationship in multi-component lifestyle interventions.