Efectos de la condición física y la adiposidad sobre indicadores de salud cardiovascular en niños y adolescentes: estudio longitudinal up&down

Abstract

Cardiovascular diseases (CVD) are the leading cause of global mortality. Normally, cardiovascular alterations become visible after the fifth decade of life, but increasing evidence suggest that their origin may occur in early ages. Thus, the identification of children and adolescents at higher risk is of vital importance for the prevention of CVD. In this sense, the definition of young people at risk of CVD is normally based on the levels of several factors, including waist circumference, triglycerides, highdensity lipoprotein-cholesterol, blood pressure (BP), and glucose levels, among others. Nonetheless, the identification of those at risk using these markers would entail a high economic cost, in addition to subjecting young people to invasive measures. Physical fitness, specifically cardiorespiratory (CRF) and muscular fitness (MF), and fatness are considered key elements for the cardiovascular risk identification, given their close association with the previously mentioned markers. Both, fitness and fatness provide a quicker and relatively simple way to identify those at risk of future CVD. However, although their association with CVD risk factors has been previously examined, their independent and combined effect on CVD risk factors remain to be fully determined. More information is needed since fitness and fatness may lay in the same causal chain leading to future CVD. Thus, the main aim of the present International Doctoral Thesis was to study the independent and combined effects of different components of physical fitness and fatness on CVD risk factors levels, cross-sectionally and longitudinally (two-year follow-up), in a sample of Spanish children and adolescents. The results of the eight studies included indicate that body mass index (BMI) is an independent predictor of CVD risk factors, and a mediator in the association of CRF (Study I) and MF (Study II) with clustered CVD risk factors. Different fitness cut-off points associated with reduced CVD risk two-years later have been identified for CRF in children (Study III) and for upper- and lowerbody MF in children and adolescents (Study IV). A bidirectional longitudinal association was observed between CRF and different fatness indicators in children and adolescents, but the associations between CRF as exposure and fatness weakened when fatness at baseline was considered (Study V). The bidirectional associations between CRF (Study VI) and MF (Study VII) with neck circumference (NC) were only observed cross-sectionally. Longitudinally, only NC showed an independent association with CRF and MF. Furthermore, BP measures seem to be longitudinally affected to a higher extent by NC than by CRF (Study VI) and MF (Study VII). Finally, waist circumference, but neither CRF nor MF, is independently associated with future BP and its changes over two years (Study VIII). The results from the present thesis enhance our knowledge on the combined and independent effects of fitness and fatness on CVD risk factors. In addition, it provides fitness cut-off points for the identification of those children and adolescents at a higher risk of future CVD.