Physical activity, sedentary time and sleep duration: associations with body composition in 10–12-year-old Estonian schoolchildren

BACKGROUND: Physical activity, sedentary time, and sleep duration have been associated with body composition among children. The purpose of the present study was to assess the associations of objectively determined daily physical activity, sedentary time, sleep duration and body composition indices in 10–12-year-old children. METHODS: Two hundred and eleven schoolchildren (96 boys and 115 girls) aged 10.9 ± 0.7 years participated in this study. Objective physical activity intensity and sedentary levels were measured for seven days by accelerometry. Sleep duration was self-reported. Percentage of body fat, waist-to-height ratio and fat free mass were calculated from measured anthropometric parameters. Multiple linear regression models were used to examine the associations between sleep duration, moderate-to-vigorous physical activity (MVPA), vigorous physical activity (VPA) level and body composition indices. RESULTS: Boys exceeded girls (p < 0.05) in time spent in MVPA and VPA levels. Only 4.3% of the children met the current daily recommendation of at least 60 min MVPA per day. Sleep duration, MVPA and VPA had a negative association with percentage of body fat and waist-to-height ratio. Vigorous physical activity had a positive association with fat-free mass. Sedentary time had a positive association with percentage of body fat and negative association with fat-free mass. CONCLUSIONS: The present study suggests that both sleep duration and MVPA are associated with body composition parameters. Higher levels of MVPA are associated with lower percentage of body fat and waist-to-height ratio regardless of sleep duration. Sedentary time is associated with higher values of percentage of body fat and lower fat-free mass independently of sleep duration.