Path analysis of environmental and genetic influences on blood pressure

Familial aggregation of a trait (determined by the intraclass correlation coefficient) may result from genetic influence or from environment common to a household. The authors used path analysis to separate aggregation into the proportion of population variability due to genetic influence (h2 = heritability) and the proportion due to environment common to a household (c2). They used data from full siblings and maternal half siblings, aged two to 18 years, from Bogalusa, Louisiana, a biracial community. The statistically significant aggregation they found could be explained by either h2 or c2 except for two cases: systolic measurement in the pooled (black and white) sample requires h2; diastolic measurement in the white sample requires c2. The authors present a simplified explanation of the techniques they used.