Adolescent Time Use and Cardiometabolic Health: A Cross-Sectional Compositional Analysis to Explore Associations Between 24-Hour Activity Behaviors and Biomarkers of Cardiometabolic Health.

Purpose: The health effects of time spent in daily activity behaviors, such as sleep, sedentary time, standing, light-intensity physical activity (LIPA), and moderate-to-vigorous intensity physical activity (MVPA), have been widely examined. Typically, these behaviors have been studied in isolation. However, daily time is composed of activities undertaken in a fixed 24-hour cycle; thus, time spent in each activity behavior is codependent. A focus on increase in one behavior in isolation ignores the consequent changes in time spent in other behaviors. This study aimed to examine the relationship between adolescent activity behaviors and indicators of cardiometabolic health by using compositional data analysis.

Methods: Participants (N = 222; 16.3 years [0.92], mean [±standard deviation]; 49% male) provided measures of body composition (height, weight, waist-to-hip ratio, 4-site skinfold thickness), cardiorespiratory fitness [CRF], grip strength, blood pressure [BP], blood lipids (low-density lipoprotein cholesterol [LDL-C], high-density lipoprotein cholesterol [HDL-C], total cholesterol [TC], and triglycerides) and markers of glucose control. Device-based measures of activity behavior were obtained from the activPAL 3 micro. Compositional linear regression models were used to examine the relationship between activity behaviors and health indicators while controlling for age, sex, and school location.

Results: LIPA (relative to the remaining behaviors) was associated with the sum-of-skinfold thickness (β = -13.9; p < .05), CRF (β = 3.9; p < .05), and diastolic BP (β = -8.3; p < .05). Sedentary time and standing time were associated with lower grip strength (β = -5.4; p < .05) and LDL-C (β = -0.38; p < .05), respectively. MVPA was associated with HDL-C (β = 0.7; p < .05) and triglycerides (β = -0.1; p < .05). Reallocating 30 minutes from sleep, sedentary time, or standing time to LIPA or MVPA was associated with significant improvements in cardiometabolic health indicators.

Discussion: This is the first study to apply compositional data analysis in adolescents that has included all activity behaviors on the physical activity continuum. The findings reinforce the health benefits of MVPA for adolescents but also provide evidence to support that increasing LIPA and standing through decreasing sitting time will improve measures of adiposity, CRF, diastolic BP, and LDL-C. Future interventional research is required to confirm the present findings.