Influence of cardiorespiratory fitness on the association between C-reactive protein and metabolic syndrome prevalence in racially diverse women

Background: Metabolic syndrome and C-reactive protein (CRP) are independent predictors of cardiovascular disease (CVD) among women. The extent to which cardiorespiratory fitness influences the relationship between CRP and metabolic syndrome is unknown. Methods and results: Cross-sectional associations among fitness, CRP, and metabolic syndrome were examined in 135 African American, Native American, and Caucasian women (55 ± 11 years, 28 ± 6 kg/m²). Fitness was quantified with a symptom-limited maximal treadmill exercise test. Plasma CRP concentrations were determined with the Dade-Behring high-sensitivity immunoassay. Metabolic syndrome was defined according to NCEP-ATP III. Metabolic syndrome, CRP, and fitness varied (p < 0.05) by race. Race-adjusted CRP values were directly associated (p < 0.05) with each metabolic syndrome component. After adjusting for age and race, the relative odds of metabolic syndrome was 3.6 (95% CI = 1.5 - 8.4) in women with elevated (>2.0 mg/L) vs. low CRP. Adjustment for smoking, hormone therapy, body mass index (BMI), and HOMA insulin resistance did not eliminate this association (p < 0.05). The association between CRP and the metabolic syndrome was no longer significant (OR = 1.3,95% CI = 0.9 - 5.9, p = 0.59) after adjustment for fitness. Conclusions: Higher cardiorespiratory fitness may be an important consideration in the milieu of vascular inflammation and metabolic syndrome.