Admixture analysis of high density lipoprotein cholesterol distribution in a Jerusalem population sample

Publisher Website
Google Scholar
Abstract
The distribution of high density lipoprotein cholesterol values (HDL-C) in 2003 nuclear families (including both parents and 1 child aged 17) participating in the Jerusalem [Israel] Lipid Research Clinic survey was analyzed by a maximum-likelihood procedure for the evidence of bimodality. HDL-C was age-sex adjusted by the mean-variance method to 17-yr-old male levels. After covariance adjustment for Quetelet''s index, season, education and social class, when using untransformed data a mixture of 2 distributions fitted the data significantly better than one distribution in both sexes. Evidently 4.7% of males and 14.1% of females came from an upper distribution with mean values of 2.15-3.15 standard deviations above the major mode. The MacLean et al. method of transformation was applied and a maximum-likelihood method was used in which the skewness parameter was estimated jointly with the other parameters of the model. When the data were transformed the mixture of 2 distributions fitted the data significantly better than one for males only. A mixture of 3 normal distributions was tested and it was estimated that 6% of both males and females belonged to a higher distribution, while 1% came from a lower distribution. This model did not provide a significantly better fit to the data than a mixture of 2 distributions. In the Israeli population there is evidence for an admixture in the distribution of HDL-C. Segregation analysis is necessary to determine whether a major gene or some environmental factors are responsible for the commingling detected.