Age-related change in children's physical activity and sedentary time: The International Children's Accelerometry Database (ICAD)

Abstract

Background Many young people fail to achieve the minimum recommended amount of physical activity to benefit their health. Understanding the nature of age-related changes in behaviour and how this varies for population sub-groups is informative for intervention design. The aim of this study was to describe age-related changes in physical activity and sedentary time and examine variability in patterns of change across demographic sub-groups. Methods Data are from 13 studies in the International Children’s Accelerometry Database (ICAD), all of which provided ≥2 waves of waist-worn accelerometer data. Annual change in sedentary time, light intensity physical activity (LPA) and moderate to vigorous intensity physical activity (MVPA) were estimated using three level mixed effects linear regression models, using participant age as the exposure variable. In interaction models, we examined whether changes in behaviour differed by day of the week (weekday/ weekend), age at baseline assessment (<10/≥10 years), sex, weight category, maternal education and ethnicity.