Abstract

In a sample of 465 families living in a suburb of north-west London the systolic and diastolic blood pressure consistently showed a greater correlation for sib/sib (0.16 to 0.28) than for parent/offspring (0.07 to 0.18); this pattern is consistent with the hypothesis of a dominance component in the inheritance of blood pressure assuming there is no difference in the interaction between environment and genes in people of different ages. This assumption was examined by studying the sib/sib correlation according to the age gap between sibs; for diastolic blood pressure this remained almost the same but for systolic blood pressure the correlation tended to diminish as the age gap increased. A dominance component in the inheritance of blood pressure levels could explain the sort of results we have found in this study. However, we cannot ignore the fact that similar results could be obtained if the contribution of the environment within the same generation of relatives differs from that of the environment shared by all relatives.