Date of Award

1-1-2010

Document Type

Campus Access Dissertation

Department

Exercise Science

First Advisor

Russell R. Pate

Abstract

This project consists of three studies that were undertaken to better understand 1) the association between accelerometry-based physical activity (PA) and a score representing CVD risk, in a population-based sample of US adolescents, 2) the association between PA -derived from self-reported and pedometers- and a score representing CVD risk, in a multi-center sample of youth with Type 1 (T1DM) and Type 2 (T2DM) diabetes and 3) the longitudinal association between change in cardiorespiratory fitness (CRF) and the development of metabolic syndrome (MetSyn), in a large population of adolescents and young adults aged 16 to 35 years, followed over an average of 6 years. The three studies also accounted for the potential confounding effect of central adiposity. For the study of CVD risk a score was created relative to the cut-offs proposed by the International Diabetes Federation to identify MetSyn. In study the mean CVD risk score was lower among adolescents with MVPA levels above the population median (24.6 minutes) vs. those with lower MVPA levels, even after adjustment by abdominal adiposity (-1.62 vs. -1.50; p= .04). In study two mean CVD risk scores decreased across quartiles of 30-minute blocks of MVPA/day and steps/day among T1DM (p for trend 0.04 and 0.19, respectively) T2DM youth without comorbidities with high vigorous physical activity (VPA) or steps/day showed lower CVD risk scores vs. youth with lower VPA or steps/day (p=0.04 and 0.09; respectively). In study three, subjects with decreasing CRF (more than 10%) had higher multivariable-adjusted risk of developing MetSyn compared to subjects with stable CRF (HR 2.09, 95% CI 1.46 - 2.99). Subjects going from "Unfit" to "Fit" had lower risk of developing MetSyn compared to individuals staying "Unfit", even after adjusting by baseline and change in abdominal adiposity (HR 0.53; 95% CI 0.30 - 0.99). In conclusion, large individual and population benefits might be achieved by helping youth with and without DM transition out of states of low CRF and low daily PA engagement. Adequate PA and CRF levels have a prominent role in the primary and secondary prevention of CVD in youth and their protective effects are largely independent of abdominal adiposity.

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