WHOLE-BLOOD PLATELET-AGGREGATION PREDICTS IN-VITRO AND IN-VIVO PRIMARY HEMOSTATIC FUNCTION IN THE ELDERLY

Increased platelet aggregation is associated with higher coronary arte ry disease mortality. Enhanced platelet aggregation in platelet-rich p lasma has also been described in the elderly. To define age-related ch anges in primary hemostasis, we studied 37 elderly and 31 young blood donors. There were no significant age-related differences in whole-blo od platelet aggregation, platelet adherence and thrombus formation on human umbilical artery segments, or bleeding time. Plasma fibrinogen w as significantly higher in elderly men and women, whereas activated fa ctor VII was elevated only in elderly women. Collagen-induced platelet aggregation was significantly correlated with platelet adherence to t he subendothelium in elderly (r=.488, P=.002) but not in young donors. Accordingly, collagen-induced platelet aggregation showed a significa nt inverse correlation with bleeding time only in the elderly (r=-.401 , P=.014). Arachidonic acid-induced platelet aggregation was significa ntly associated with platelet adherence to the subendothelium (r=.658, P=.003) and bleeding time (r=-.540, P=.021) only in elderly men. In y oung donors, ADP-induced platelet aggregation was significantly correl ated with platelet adherence to the thrombogenic adventitial surface ( r=.395, P=.031); in the elderly this association only approached signi ficance (r=.315, P=.058). Whale-blood platelet aggregation in response to collagen and arachidonic acid may be more useful in predicting pri mary hemostatic function in the elderly than in the young. Furthermore , in the elderly, the correlation between platelet aggregation in whol e blood and platelet-arterial wall interactions in vitro and in vivo m ay contribute to the ability of this test to predict coronary risk.