Covariance of metabolic and hemostatic risk indicators in men and women

Background and objective: Multivariate analyses on clusters of metabolic an d hemostatic risk indicators implicitly assume good test-retest reliability of these variables, substantial covariance among the various indicators, s tability of covariance structure over time, and comparable covariance struc ture in different subpopulations. The aim of the present study is to invest igate these assumptions. Methods: Repeated samples were taken of fasting insulin, triglycerides (TG) , high-density cholesterol (HDL-C), low-density cholesterol (LDL-C), fibrin ogen, tissue-type plasminogen activator (t-PA) antigen, t-PA activity, plas minogen activator inhibitor-1 (PAI-1) antigen to address their intra-week r eliability and covariance structure. In the same work-week blood was drawn three times from 125 sedentary males (age 45.2 +/- 5.3 years) and twice fro m 132 female nurses (age 33.7 +/- 8.0 years). Results: About half (44.8%) of these women were oral contraceptives (OC) us ers. Only minor intra-week changes in absolute levels were found. Intra-wee k test-retest correlations varied between 0.52 (t-PA activity) and 0.94 (HD L-C) with an average value of 0.81. In men, non-OC using women, and OC usin g women, the covariance matrices of the eight risk indicators were equal at day 1 and day 3, testifying the good stability of covariance structure ove r time. Differences in covariance structure of all three groups were observ ed, which remained after correction for BMI and age. In men and non-OC-usin g women, significant correlation was found on all days between insulin and the other risk indicators with exception of fibrinogen and LDL-C. In OC use rs, insulin was correlated with TG, LDL-C, and fibrinogen. Conclusion: The metabolic and hemostatic risk indicators showed good test-r etest reliability, and their covariance is stable over time. Multivariate a nalyses of this cluster should be performed separately for men, non-OC-usin g women, and OC-using women. (C) 2001 Harcourt Publishers Ltd.