Sedentarism and Physical Inactivity Patterns Correlated with HOMA-IR in European Adolescents, the Helena Study

Abstract

Objective: The aim of the present study was to examine the independent association between time spent on sedentary activity, either objectively measured or self-reported and IR proxy measures in European adolescents. Methods:A subset (n=1,097) of a large multicentre European study in adolescents (HELENA-CSS study) was used in the present study. Homeostasis model assessment (HOMA)-IR was calculated. Serum concentrations of glucose (GF) and insulin (IF) were measured after an overnight fast. The HOMA-IR was calculated as IF (µlU/mL) × GF (mmol/l)/22.5 (to convert IF values in µlU/mL to pmol/l multiply by 6.945) sedentary time and the time spent on moderate-to-vigorous physical activity (MVPA) was objectively measured by using accelerometers. Moreover, the daily minutes spent on sedentary activities were recorded through a self-report sedentary behaviour questionnaire.Results: Univariate analyses showed that HOMA-IR levels were significantly higher among adolescents watching TV ≥ 2h/day (1.87 (C.I.1.31, 2.66)) compared to the rest of adolescents (2.02 (1.44, 2.82), p=0.011). Moreover, the objectively measured MVPA was inversely correlated to HOMA-IR (rho=-0.117, p=0.023). Multilevel linear regression analysis revealed that adolescents watching TV ≥ 2 h/day had significantly higher HOMA-IR even after controlling for gender, age, total energy intake, total fat intake, simple carbohydrate intake and pubertal stage (p=0.007). Further adjustment for MVPA, showed that TV viewing time remained significantly related to the IR (p=0.002). In this model, MVPA was also inversely associated with HOMA-IR levels (p=0.001). Finally, further controlling for waist circumference showed that adolescents exceeding the limit of 2 h/day watching TV continued to have higher HOMA-IR levels (p=0.002). Stratified analysis by BMI status, revealed that TV viewing time is independently associated with HOMA-IR only among normal weight adolescents, while MVPA was inversely associated with IR in both overweight/ obese and normal weight adolescents. Conclusions:The results of the present study indicate that time spent watching TV and at MVPA is related to IR independent of central fat mass and total energy intake in normal weight European adolescents, while MVPA seems to protect adolescents from developing IR even among overweight/obese adolescents. Therefore, intervention programmes aiming at reducing sedentary behaviours and increasing overall moderate-intensity activities should be implemented.