Heredity, stress and blood pressure, a family set method-V. Heritability estimates

This fifth article in the series, reports on a general method for estimating heritabilities based upon family sets, illustrated for a particular family grouping, namely, one which consists of an index person, his or her sibling, first cousin, and a randomly selected unrelated individual. This method is applied to the estimation of the heritabilities of systolic and diastolic blood pressure in the presence of extraneous concomitant variation as well as classificatory variables of interest. Analysis fails to disclose significant racial differences in the heritability of these two pressures, and indeed, suggests that in both blacks and whites, nongenetic variables contribute more to the variation in blood pressure which is observed than do genetic differences between individuals. It is argued that the difference between these findings and those associated with some prior investigations is attributable to ascribing effects to genetic causation, which in fact were due to shared environments or temporal trends.