Environmental and genetic sources of familial aggregation of blood pressure in Tecumseh, Michigan.

Environmental and genetic sources of variation in blood pressure have been assessed for an 82% sample of the Tecumseh, Michigan, population during the period 1962-1965. Correlations of systolic blood pressure and diastolic blood pressure were calculated for sets of related and unrelated individuals living together and related individuals living apart. These correlations were analyzed using a biologic model which partitions the total phenotypic variance into components associated with shared genes and components associated with shared household environments both within and across generations. Heritabilities were estimated to be 0.42 and 0.30 for systolic blood pressure and diastolic blood pressure, respectively. The model confirms the hypothesis that the determinants of blood pressure consist of both significant genetic (p less than 0.005) and environmental (p less than 0.005) components. However, only the shared household environments within generations were found to be significant for systolic blood pressure (p less than 0.005) and diastolic blood pressure (p less than 0.05). Although not significant, the across generation shared environment between mothers and offspring tended to have some importance, while that between fathers and offspring was negligible. The implication that there may be some maternal influence in addition to the genetic influence on the determination of blood pressure in offspring warrants further investigation.