Abstract MP030: The Association Between Objectively Measured Sleep, Physical Activity and Sedentary Behaviour on Cardiorespiratory Fitness and Health in 9 - 11 Year Old New Zealand Children

Abstract

Background: The role of activity, sedentary behaviour and sleep in cardiorespiratory fitness (CRF) or cardiovascular health, has been primarily studied in adults. Therefore we assessed the hypothesis that longer sleep duration, more time spent in moderate to vigorous activity (MVPA), less sedentary time and a lower ratio of sedentary time to MVPA (Sedentary: MVPA) would be associated with higher CRF and lower pulse wave velocity (PWV) in children aged nine to 11 years from Dunedin, New Zealand. Methods: A cross-sectional study. Information on demographics and lifestyle was collected by questionnaire. Data on sleep, sedentary and MVPA time were collected using Actigraph wGT3X-BT accelerometers, worn over eight days. PWV was obtained using the SphygmoCor Xcel. VO 2 max values, from a multi-stage 20-metre shuttle run test, were used as the measure of CRF. Generalised estimating equations were undertaken to investigate relationships between accelerometer derived variables and CRF and PWV separately in 404 participants. Analyses were adjusted for age, socioeconomic status, ethnicity and age and sex specific BMI Z scores. Results: Mean (SD) VO 2 max was 47.5 (4.1) Ml/Kg/min for girls and 49.9 (5.20) for boys and mean (SD) PWV was 5.72 (0.79) for girls and 5.85 (0.79) for boys. In multivariate models, a one hour increase in sedentary time was associated with a 0.81 (CI: -1.19, -0.42) Ml/Kg/min increase in VO 2 max in all participants. In boys only, a one hour increase in MVPA associated with a 3.50 (CI: 2.76, 4.20) Ml/Kg/min increase in VO 2 max. Sedentary: MVPA was associated with lower VO 2 max in boys and girls. Sedentary time (β 0.15 m/s per hour increase, CI: 0.02, 0.27) and MVPA (β 0.25 m/s per hour decrease, CI: 0.04, 0.46) were only significantly associated with PWV in boys. No significant assocaitions were seen between sleep and CRF or PWV. Conclusions: In conclusion, sedentary behavior, MVPA and Sedentary: MVPA were both associated with CRF and PWV. Our results suggest that future interventions aimed at improving heart health in this age group need to target both increasing physical activity and reducing sedentary time. Funding sources: The National Heart Foundation of New Zealand and The University of Otago.