Age- and Sex-Specific Reference Percentile Curves for Accelerometry-Measured Physical Activity in Healthy European Children

Abstract PURPOSE: Physical activity measured by accelerometry (PA-accelerometry) is used as an indicator of disease severity in chronic diseases. Currently, only fragmented age ranges of reference percentile curves are available for European children. This study aimed to provide age- and sex-specific percentiles for physical activity measured by hip-worn accelerometry derived throughout the full age range of European children. METHODS: Individual-level population-based PA data from HELENA and IDEFICS/I.Family studies were pooled and harmonized. Together these studies involved children aged 2–18 years from 12 European countries. PA was measured using uni-axial or tri-axial Actigraph accelerometers. Accelerometry recording was defined as valid if lasted at least 6 hours on at least 2 weekdays and 1 weekend day. Primary outcomes included averaged counts per minute (CPM), sedentary time (SED), light PA (LPA) and moderate-to-vigorous PA (MVPA). Generalized Additive Models for Location, Scale and Shape were used to derive age- and sex-specific reference percentile curves for these outcomes. RESULTS: The combined cohort consisted of 11,645 children aged 2 to 18 years who contributed 14,610 valid accelerometry recordings, with a median accelerometer wear time of 6 days and a median wear time of 745 minutes per day. This dataset allowed for the construction of age- and sex-specific reference percentile curves for CPM, SED, LPA, and MVPA. The curves demonstrated varying trends and variability across age groups. CONCLUSIONS: This study provides age- and sex-specific percentile curves for PA-accelerometry in European children, addressing a current gap in the availability of full-age range reference data. These curves based on healthy children can be used by clinicians, researchers, and policymakers to interpret PA-accelerometry measurements, assess severity of disease in paediatric chronic illness, track physical activity trends, and evaluate treatment responses and health interventions.