Child opinions related to a core outcome set for school-based healthy lifestyle behavior interventions: the COCOS study

Introduction: Including children's perspectives developing health programs is a priority. This study gathered children's perspectives on outcomes in a Core Outcomes Set (COS), which they believe are important to measure in school-based healthy lifestyle behavioral interventions. Methods: Children aged 8–12 years from six countries across three continents participated in standardized interactive focus groups. An animation video was used to explain all relevant concepts (e.g., “intervention”, “outcomes”) and showed animated children engaging in a variety of lifestyle behaviors at school. Participating children then brainstormed and proposed outcomes they consider important to measure when evaluating a school-based “healthy lifestyle programme”. Next, children individually rated the importance of the outcomes using a traffic light system (red, “not important”; orange, “important”; green, “very important”). Similar outcomes (across focus groups and countries) were merged, and an overall importance rating was given to each outcome (across countries and overall). An outcome was considered important for inclusion in a COS if ≥70% of children scored the outcome as “very important” and