Familial aggregation of blood pressure, anthropometric characteristics and urinary excretion of sodium and potassium--a population study in two Belgian towns.

Blood pressure and anthropometric characteristics were measured on two separate occasions and the urinary sodium and potassium excretion determined from one 24-hr urine collection in a random population sample (n = 612) of two Belgian towns. After adjusting for confounding factors familial aggregation of these measurements was studied by computing correlation coefficients for the various intrafamilial relationships. Spouses are genetically dissimilar and share a common home environment only from adulthood on. The spouse-spouse correlations for blood pressure, body weight, body mass index and urinary sodium were therefore not significant, whereas the close spouse-spouse correlation for height (r = 0.29) may be explained by assortive marriage. Sibs not only share a common home environment, but also part of their genetic material. Significant sib-sib correlations could therefore be demonstrated for diastolic blood pressure (r = 0.21), height (r = 0.32), body mass index (r = 0.24) and urinary sodium (r = 0.34). For systolic pressure the father-son (r = 0.33) and mother-daughter (r = 0.24) correlations were significant, whereas the other parent-offspring correlations for systolic and diastolic pressure were not statistically different from zero. The tendency of the correlation coefficients for body weight and body mass index to be higher in mother-offspring than in father-offspring pairs suggests a closer maternal role in the determination of calorie intake in offspring. The parent-offspring correlations for urinary sodium were only significant in father-daughter (r = 0.24) and mother-son (r = 0.21) pairs. The fact that potassium, in contrast to sodium, is rarely used as an artificial additive in food preparation may explain why the correlations for urinary potassium were relatively high in all relationship pairs, varying from 0.20 to 0.34.