Does the intervention of the school-based health promotion programme "Join the Healthy Boat" have equal or differential effects on weight status and health-related behaviours in children from a high or low socio-economic background? - A randomised controlled trial

Background: Worldwide, the prevalence of childhood overweight and obesity increases. Children with low socioeconomic status (SES) are more often affected by overweight and obesity. SES is also associated with health behaviours. In order to avoid health disparities, school-based health promotion programmes such as "Join the Healthy Boat" can help. Intervention outcomes can differ by SES; therefore, the purpose of this study was to investigate whether the intervention had equal or differential effects both on weight status and health-related behaviours in children from high and low SES.

Methods: One thousand six hundred twenty children's data (7.1 ± 0.6 years; 50.6% male) was analysed; anthropometric data was taken on-site, other health-related parameters, such as physical activity, nutrition, and screen media use, as well as SES were assessed subjectively. Logistic regression models and GEEs were calculated.

Results: Comparisons by SES show that there were significant differences in children's characteristics and health behaviours such as migration background, height, weight, BMI percentiles, weight status, family education level, household income, physical activity behaviour, screen media use, soft drink intake and breakfast skipping. After one year, there were no intervention effects for overweight status, physical activity, or screen media use, but children with high SES in the intervention group skipped breakfast significantly less often than in the control group (5.34 [1.44;19.85], p = 0.01). Parental education level and household income were also assessed separately, with similar results. Interaction analysis revealed no significant effects apart from an interaction effect for breakfast behaviour (p = 0.02).

Conclusions: The health-promotion programme "Join the Healthy Boat" has the potential to promote children's health via a school-based intervention and therefore, reach all children independent from their background. This study shows vast gaps between several health behaviours of primary school children depending on their SES, favouring those children coming from more privileged families. A longer implementation may possibly show more effects.

Trial registration: DRKS00000949.