Covariance of metabolic and hemostatic risk indicators in men and women

Abstract

Background and objective: Multivariate analyses on clusters of metabolic and hemostatic risk indicators implicitly assume good test–retest reliability of these variables, substantial covariance among the various indicators, stability of covariance structure over time, and comparable covariance structure in different subpopulations. The aim of the present study is to investigate these assumptions.Methods: Repeated samples were taken of fasting insulin, triglycerides (TG), high-density cholesterol (HDL-C), low-density cholesterol (LDL-C), fibrinogen, tissue-type plasminogen activator (t-PA) antigen, t-PA activity, plasminogen activator inhibitor-1 (PAI-1)antigen to address their intra-week reliability and covariance structure. In the same workweek blood was drawn three times from 125 sedentary males (age 45.2±5.3 years) and twice from 132 female nurses (age 33.7±8.0 years).Results: About half(44.8%) of these women were oral contraceptives (OC) users. Only minor intra-week changes in absolute levels were found. Intra-week test-retest correlations varied between 0.52 (t-PA activity) and 0.94 (HDL-C) with an average value of 0.81. In men, and non-OC using women, and OC using women, the covariance matrices of the eight risk indicators were equal at day 1 and day 3, testifying the good stability of covariance structure over time. Differences in covariance structure of all three groups were observed, which remained after correction for BMI and age. In men and non-OC-using women, significant correlation was found on all days between insulin and the other risk indicators with exception of fibrinogen and LDL-C. In OC users, insulin was correlated with TG, LDL-C, and fibrinogen.Conclusion: The metabolic and hemostatic risk indicators showed good test-retest reliability, and their covariance is stable over time. Multivariate analyses of this cluster should be performed separately for men, non-OC-using women, and OC-using women.