Borderline hypertension--a critical review.

INTRODUCTION THIS REVIEW explores a poorly-defined area of borderline abnormal blood pressures. Different definitions as to what is normal and abnormal blood pressure traditionally apply sharp cutting lines, but they differ from study to study. No one would question that consistent readings below 130/80 represent normal blood pressure, and those always above 160/100 at any age require medical attention. However, the significance of readings falling between these limits may be questioned. The situation becomes more confused when the readings oscillate between the entirely normal and quite abnormal range. The medical significance of this condition is even more uncertain. Evidence from the literature based on heterogeneous data ranges from a tentative indictment of borderline hypertension as a precursor of hypertensive disease [l] to a view supporting a more favorable outlook [2]. This report will review some of the evidence on the epidemiology, clinical characteristics, and pathophysiology of borderline hypertension. Since the nomenclature and type of measurement used in different studies are variable, we will define borderline hypertension as broadly as possible. We will review papers describing subjects in whom: A. Blood pressure readings over 150/90 were intermittent and occasional normal readings were obtained. B. Average or single readings were below 160/100 but above 150/90. C. There was no evidence of target organ damage. Exceptions will be made for some important papers not adequately characterizing the population but dealing with subjects we believe had borderline hypertension. The traditional division into 'established' and 'labile' blood pressure will not be pursued in this review, chiefly, because the lability can not be defined accurately and it depends greatly on the number and circumstances of the determination. If the subjects described in a paper fit our criteria, we will call them 'borderline hypertension' irrespective of the original nomenclature. To facilitate this review data on definitions, characteristics of the population and methods of measurement in the major papers are not presented in the text. 723