Variations in coagulation factors in women: Effects of age, ethnicity, menstrual cycle and combined oral contraceptive

To assess variations of coagulation factors in women, 123 women were includ ed in a cross-sectional study of the effect of age, ethnic origin, blood gr oup and menstrual cycle on surface induced coagulation time (activated part ial thromboplastin time) and plasma levels of Factor VIII clotting assay, v on Willebrand factor antigen, von Willebrand factor activity and factor XI. The effect of menstrual cycle was further assessed in a longitudinal study including 39 Caucasian women, 20 of whom were using combined oral contrace ptives. Activated partial thromboplastin time was longer in women with bloo d groups B or O, and plasma levels of factor VIII clotting assay, von Wille brand factor antigen and von Willebrand factor activity were significantly higher in black women. Fibrinogen, von Willebrand factor antigen and von Wi llebrand factor activity concentrations showed strong cyclic variations wit h peak values in the luteal phase. This pattern was dampened for von Willeb rand factor antigen and von Willebrand factor activity but completely disap peared for fibrinogen with the use of combined oral contraceptives. There w as a cyclical pattern for factor VIII clotting assay in pill users, evidenc e of which was not evident in non-pill users. There were strong association s between the levels of von Willebrand factor antigen and von Willebrand fa ctor activity and age, with levels rising by an average of 0.17 and 0.15 U/ ml, respectively, for each 10 year increase in age. In conclusion, there ar e great inter- and intraindividual variations in coagulation markers in wom en due to different physiological conditions such as age, ethnicity, blood group and phases of the menstrual cycle. However, there were no significant associations between coagulation markers and weight, alcohol consumption o r smoking status.