Compliance With The 24-h Movement Guidelines In Hong Kong Adolescents: Associations With Body Mass Index

The evidence-based 24-h Movement Guidelines (MG) for children and youth was launched in 2016, shifting the thinking from one single movement behavior to an integration of three behaviors under the 24-h circle: physical activity (PA), screen time (ST), and sleep. A low compliance rate of meeting these combined recommendations has been reported for children. However, few studies have focused on adolescents, and its association with health outcomes such as body weight status is largely unknown. PURPOSE: To examine compliance with the 24-h MG among Hong Kong adolescents and their associations with body mass index (BMI). METHODS: 1,039 adolescents (11-18 yrs) wore the waterproof activPALTM for 24-h over 7 consecutive days to assess PA and sleep duration. ST was measured using items from the validated Chinese version of the Children's Leisure Activities Study Survey. Participants were classified into 8 categories depending on the adherence to the 3 recommendations: none, single recommendation (PA, ST or sleep), two recommendations (PA & ST, PA & sleep, or ST & sleep) and all three recommendations. BMI was calculated as weight (kg) / height (m)2. Linear mixed models were used to examine the associations of BMI with the 8 categories and the number of guidelines met (0~3), adjusted for age, sex and school clustering effects. RESULTS: The analytic sample consisted of 656 adolescents (48% of girls) who provided valid activPALTM data for at least 4 days and completed questionnaire. Only 1.1 % of the adolescents met the overall 24-h MG, while 38.7% met none of them. The proportion of meeting one single recommendation of PA, ST and sleep was 9.9%, 30.3% and 39.2%, respectively. Adolescents who did not meet the PA recommendation (b = 1.34; 95% CI, 0.32 to 2.36; p = 0.007) and those who did not met the combination of PA and sleep recommendations (b = 2.15; 95% CI, 0.49 to 3.82; p = 0.011) had higher BMI than those who met the respective recommendations. No significant association was found between number of recommendations met and BMI. CONCLUSIONS: Compliance with the 24-h MG was alarmingly low among Hong Kong adolescents. Meeting PA recommendation and the combination of PA and sleep recommendations were more likely to have a healthier body weight. Supported by the General Research Fund of the Research Grants Council, Hong Kong, China (#14501415).