Physical activity, sedentary time, TV viewing, physical fitness and cardiovascular disease risk in adolescents: The HELENA study.

BACKGROUND: To examine the independent associations between physical activity (PA) intensities, sedentary time (ST), TV viewing, cardiorespiratory fitness (CRF) and muscular fitness (MF) with cardiovascular disease (CVD) risk in youth.

METHODS: A cross-sectional study on 534 European adolescents (252 males, 282 females, 12.5-17.5years). Minutes per day of light (LPA), moderate (MPA) and vigorous (VPA) PA and total ST were measured using accelerometers. TV viewing time was measured using a questionnaire. CRF and MF were measured using the 20m shuttle run test and a hand dynamometer respectively. CVD outcomes included markers of body composition (body mass index (BMI), waist circumference (WC), WC/height (Ht) and sum of skinfolds (SumSF)), blood pressure, blood lipids and insulin resistance (HOMA-IR). Clustered CVD risk was calculated using SumSF, HOMA-IR, blood lipids and blood pressure.

RESULTS: LPA had a significant positive independent relationship with all body composition outcomes (P<0.001) and clustered CVD risk (P=0.046). VPA was negatively related to SumSF (P<0.001), BMI (P=0.018), WC/Ht (P=0.013) and clustered CVD risk (P=0.001), but was non-significant for all when other exposures were considered (P>0.10). MPA had a negative independent relationship with only WC (P=0.029) and ST was not significantly related to CVD risk (P>0.16). TV viewing had a significant positive independent relationship with HOMA-IR (P<0.001) and clustered CVD risk (P=0.019). CRF (all P<0.002) and MF (all P<0.009) had a negative independent relationship with body composition outcomes and clustered CVD risk.

CONCLUSIONS: Public health guidelines should prioritize on increasing levels of CRF, MF and VPA, and reducing TV viewing time to lower CVD risk in youth.