Bivariate path analysis of plasma lipids

Methods which allow for the analysis of the joint transmission of two phenotypes within a nuclear family are discussed and applied to the transmission of cholesterol and triglyceride. The analysis of data from 160 Caucasian nuclear families suggests a moderate degree of both genetic and residual environmental association between the two lipids. Although either the genetic correlation (rho G) or the residual environmental correlation (rho R) could set equal to 0 without significantly increasing the residual chi 2, simultaneously setting both correlations equal to zero did significantly increase the chi 2 statistic. Consequently, the association between cholesterol and triglyceride could not be accounted for by common transmissible environmental effects alone.