Evidence for a Relationship between High Fibrinogen Levels and Decreased Thrombin Activity in vivo in Elderly Subjects

In order to investigate whether high fibrinogen levels were associated with elevated thrombin activity, we measured fibrinogen and fibrinopeptide A in 37 elderly healthy subjects ranging from 60 to 93 years. Fibrinogen levels (519.1 ± 127.0 mg/dl) and fibrinopeptide A (5.9, 0.9–18.1 ng/ml) were significantly higher than in younger controls. A highly significant negative linear correlation was found between fibrinogen and fibrinopeptide A in the elderly subjects (p < 0.01). However, a polynomial regression showed that this negative relationship was present at the fibrinogen levels ranging between 420 and 700 mg/dl. Our results suggest that high fibrinogen levels in elderly subjects do not necessarily mean that their thrombin activity is concomitantly increased.