Physical fitness and C-reactive protein level in children and young adults: The Columbia University BioMarkers Study

Objective. To examine the association of physical fitness with C-reactive protein (CRP) level in children and young adults. Methods. Subjects (N = 205) aged 6 to 24 years were enrolled in the Columbia University BioMarkers Study (1994-1998). Physical fitness was assessed using a non-effort-dependent treadmill testing protocol (physical work capacity at heart rate of 170 beats per minute). CRP level was measured using a high-sensitivity assay. Results. Subjects were 54% female and 65% of Hispanic origin. Mean fitness level was higher in boys than in girls, but CRP levels did not differ by gender. Fitness level was inversely correlated with CRP (r = -0.22). This relationship was significant in boys (r = -0.32) but not in girls (r = -0.15). After multivariate regression adjustment for age, race/ethnicity, body mass index, and family history of early-onset ischemic heart disease, physical fitness remained inversely associated with CRP level in boys (β = -0.02; standard error = 0.01). Conclusions. These findings indicate that physical fitness is inversely related to CRP level in children and that this relationship is more pronounced in boys than in girls.