A Longitudinal Study of Blood Pressure

Abstract

A longitudinal study of blood pressure in a homogeneous group of young men followed over an 18-year period has been presented. Seven hundred and eighty-five (96 per cent) of the surviving members have been re-evaluated, and the mean age at the time of re-examination was 42 years. Frequency distribution curves of blood pressure yielded a unimodal distribution and indicated that blood pressure is a graded continuous variable. There was no evidence of natural bimodal distribution to suggest emergence of a qualitatively different population. Each individual tended to maintain his relative position within the distribution curve over the period of study, but this was modified by genetic and environmental factors. Significant correlations were found between the variables of weight and somatotype. A significantly greater increase in blood pressure was noted in association with increasing weight. Subjects with a predominance of ectomorphic characteristics had a smaller increment of blood pressure over the period of study. Endomorphic subjects had a greater increment of blood pressure. The changes in blood pressure related to somatotype were modified by weight, but not dependent upon an increase in weight. A family history of vascular disease was associated with a significantly greater increase in blood pressure. The greater increment in blood pressure associated with a positive family history was not dependent upon weight gain for its influence. There was no evidence that a positive family history separated a portion of the population ranked according to blood pressure. Analysis of the upper and lower segments of the distribution curves, revealed significant differences between the characteristics of each group. These differences followed the same pattern as the entire group but were quantitatively different. These results are discussed with regard to the concept that hypertension represents a quantitative difference in blood pressure resulting from a multiplicity of factors, both genetic and environmental.