Inverse association of physical fitness with plasma fibrinogen level in children: the Columbia University BioMarkers Study.

Plasma fibrinogen has emerged as a risk factor for cardiovascular disease in adults, but relatively little is known about the correlates of plasma fibrinogen level in childhood. In the Columbia University BioMarkers Study (1994-1998), the authors evaluated the association between physical fitness and plasma fibrinogen level in 193 children 4-25 years old; 68% were Hispanic and 46% male. Fitness level assessed by treadmill testing was inversely associated with plasma fibrinogen (r = -0.24, p<0.001). Plasma fibrinogen levels showed a graded inverse relation with tertiles of fitness assessed by treadmill (p<0.001). In multivariate analyses, after adjustment for age, sex, race/ethnicity, body mass index, and presence of the A allele in the -455 position of the beta-fibrinogen promoter gene, the fitness level remained inversely associated with plasma fibrinogen level (beta = -1.3, 95% confidence interval (CI): -2.3, -0.34). Resting heart rate was also correlated with plasma fibrinogen level (r = 0.18, p<0.05). Fibrinogen levels (mg/dl) increased over tertiles of resting heart rate (p = 0.002) and were significantly associated with resting heart rate in multivariate analysis (beta = 0.82, 95% CI: 0.17, 1.5). These findings indicate that plasma fibrinogen is inversely associated with physical fitness in children independent of body mass index.