Length of sedentary breaks is associated with metabolic risk score in Portuguese children and adolescents: The LAbMed physical activity study

Purpose: To analyze the association of the length of sedentary behavior breaks on metabolic risk score (MRS) in Portuguese adolescents (12-18 years).

Methods: In 2012 we evaluated 400 adolescents (46% males) in a school-based study. We measured cardiorespiratory fitness (20m_shuttle-run test), blood pressure, height, waist circumference, fasting glucose and insulin, total cholesterol, HDL-cholesterol, triglycerides and C-reactive protein. The HOMA-IR, waist-to height and total cholesterol/HDL-cholesterol ratios were calculated. For each of these variables, a Z-score was computed by age and sex. Cardiorespiratory fitness Z score was multiplied by -1. MRS was constructed by summing all the Z scores. We also assessed sedentary behavior, physical activity (accelerometry, Evenson’s cut points), pubertal status (Tanner stages), socio-economic status (Family Affluence Scale), tobacco consumption and adherence to a Mediterranean diet (KIDMED score).

Results: Accelerometer wear time was 13.20(±1.40)h/day, of which an average of 8.78(±1.41) h/day was spent sedentary, and of 0.75(±1.36)h/day in moderate-to vigorous physical activity. Sedentary time was broken up an average of 152.2(±31.13) times/day, with a mean break duration of 1.77(±1.32)min. Linear regression analysis showed that average length of sedentary breaks was associated with MRS (β=-2.607, p=0.023) only in girls after adjusting for total sedentary time, moderate-to vigorous physical activity, accelerometers wear time, gender, socio-economic status, Mediterranean diet, tobacco consumption, age and pubertal status.

Conclusions: The length of sedentary breaks was beneficially associated with MRS, regardless of total sedentary time and moderate to vigorous physical activity.