Factor relationships of metabolic syndrome and echocardiographic phenotypes in the HyperGEN study

BACKGROUND: Metabolic syndrome and its risk factors are predictors of cardiovascular events. Metabolic syndrome is also directly associated with echocardiographic phenotypes. METHODS: The current study is the first to investigate the factors associated with both metabolic syndrome risk factors and echocardiographic phenotypes and assess their heritability. Multivariate factor analysis was performed on 15 traits in 1393 African-Americans and 1133 whites, as well as stratified by type 2 diabetes mellitus status. RESULTS: Factor analysis with varimax rotation established four to five latent factors across ethnicities and diabetes mellitus stratifications. Among metabolic syndrome risk factors, blood pressure was the most highly correlated with cardiac traits. The factor domains, in the order of the proportion of variance explained, were 'left ventricle wall thickness', 'left ventricle geometry', 'blood pressure', 'BMI-insulin', and 'lipid-insulin'. Factor analysis without any rotation identified special (cross domain) metabolic syndrome-echocardiographic factors, 'blood pressure-left ventricle geometry' and 'blood pressure-left ventricle dimension-wall thickness' in whites. Fifty to 57% of the total original risk factor variance was explained by the latent factors. Heritability was highest for BMI-insulin (37-53%), lowest for 'blood pressure' factors (15-27%), and intermediate for metabolic syndrome-echocardiographic factors. CONCLUSION: These latent factors identified can be utilized as summary phenotypes in epidemiological, linkage, and association studies.