Cardiorespiratory fitness and clustered cardiovascular disease risk in U.S. adolescents.

PURPOSE: To study the association between the cardiorespiratory fitness (CRF) distribution and cardiovascular disease (CVD) risk measured as continuous scores for individual and clustered CVD risk factors and to explore the potential effect modification of this association exerted by weight status among adolescents.
METHODS: Cross-sectional study based on 1,247 youths aged 12-19 years in the 1999-2002 National Health and Nutrition Examination Surveys. CRF was estimated by a treadmill test and categorized into age- and sex-specific quintiles. Five established CVD risk factors - an adiposity index (sum of triceps and subscapular skinfolds), the homeostatic model assessment of insulin resistance, systolic blood pressure, triglycerides, and total cholesterol/high-density lipoprotein cholesterol - were standardized for age and gender and a clustered score calculated as their average. Regression analyses adjusted for race/ethnicity and family socioeconomic status assessed differences in CVD risk across CRF quintiles for the overall sample and after stratification by weight status.
RESULTS: The mean clustered risk score decreased with increasing CRF in both males and females (p for trend <.001 and .004, respectively). The most significant decline in the clustered CVD risk score across CRF quintiles was observed from the first to the second quintiles (53.6% and 37.5%, in males and females, respectively). The association remained significant in both overweight and normal weight males and in normal weight females (p < .05).
CONCLUSIONS: Most of the excess clustered CVD risk is found among adolescents within the lowest quintile of the CRF distribution. Among adolescents, very low fitness states should be avoided or intervened upon for purposes of primordial CVD prevention.