The major findings of family aggregation of blood pressure in the Evans County Prevalence Survey are that (1) similarities for first degree genetic relatives, as measured by correlation coefficients, are of the same order of magnitude in blacks and whites and of the same order of magnitude as reported in other populations; (2) categorical, mating-type analysis applied to the data indicates the dependence of offspring prevalence of both systolic and diastolic high blood pressure upon parental type, and this is greater in the white than the black; (3) evidence from both categorical and correlational analyses indicates spouse similarity in the white pairs, not in the black pairs; and (4) for white spouse pairs aggregation is a function of wife's age and is maximal at approximately the age of 50 years.
Hayes CG, Tyroler HA, Cassel JC. Family Aggregation of Blood Pressure in Evans County, Georgia. Arch Intern Med. 1971;128(6):965-975. doi:10.1001/archinte.1971.00310240119016