TIME-DEPENDENT VARIATIONS IN THE COAGULATION-FACTOR-II, COAGULATION-FACTOR-VII, COAGULATION-FACTOR-IX, AND COAGULATION-FACTOR-X IN YOUNG AND ELDERLY VOLUNTEERS

The existence of circadian (24-h) rhythms in the coagulation activity of vitamin K-dependent coagulation factors (Factors II, VII, IX, and X ) were studied in six healthy young (18-30 years old) and six healthy elderly (69-75 years old) men. Aliquots of 5 ml of blood were obtained from each of the 12 subjects at six different time points over a 24-h period. Factors II, VII, and X were quantified by the prothrombin tim e test, whereas Factor IX was analyzed by the activated partial thromb oplastin time test. Significant circadian variations were found for Fa ctors IT and VII in both age groups, The peak and trough values for Fa ctor II were observed at 16:00 and 00:00 in young men and at 12:00 and 16:00 in elderly men. The amplitude of the rhythmic variation of Fact or II was 3.3 +/- 1.0 and 4.2 +/- 0.9% in young and elderly volunteers , respectively. For Factor VII, the highest values were found during t he activity period (08:00-16:00), while the lowest values occurred at night (00:00) for both groups of subjects. The amplitude of the rhythm s was twice as large in the young (6.2 +/- 2.3%) as in the elderly (3. 7 +/- 0.8%). The data suggest that age does not alter significantly th e chronobiology of Factors II and VII.