THE RATIONALE FOR DIFFERING NATIONAL RECOMMENDATIONS FOR THE TREATMENT OF HYPERTENSION

This article examines the rationale for the differences in the guideli nes for hypertension management of four national or international bodi es: the Joint National Committee (JNC-V), The World Health Organizatio n/International Society of Hypertension (WHO-ISH), the British Hyperte nsion Society (BHS), and the New Zealand guidelines. These guidelines agree on many aspects of management, but differ on two very important points-the drugs of first choice for hypertension, and the indications for drug treatment of uncomplicated mild hypertension. JNC-V recommen ds treatment routinely of all people with a sustained blood pressure o f 140/90 mm Hg, whereas the BHS guidelines advise treatment routinely at 160/100 mm Hg. Such differences in the threshold for treatment have a major impact on the proportion of the adult population to be treate d, and on the benefit from treatment. JNC-V was heavily influenced by the Hypertension Detection and Follow-up Program (HDFP), which appeare d to show a large benefit from the treatment of uncomplicated mild hyp ertension, whereas the BHS guidelines were influenced by the Medical R esearch Council (MRC) Trial, which showed a very small benefit. Howeve r, the apparent differences in absolute benefit between these, and oth er, randomized controlled trials is related entirely to differences in the absolute cardiovascular risk of the populations studied. In popul ations and in individual patients the benefit from antihypertensive tr eatment is determined by the absolute cardiovascular risk. Blood press ure by itself is a very weak predictor of risk or benefit from treatme nt. In uncomplicated mild hypertension the need for drug therapy shoul d be based on the absolute risk of cardiovascular complications, estim ated by considering age, sex, serum cholesterol level, diabetes mellit us status, and smoking habits, in addition to blood pressure. Doctors cannot estimate absolute risk accurately informally or intuitively, an d the next generation of guidelines should incorporate a simple but ac curate method for estimating cardiovascular risk, similar to that in t he New Zealand guidelines. The decision to treat, or not treat, uncomp licated mild hypertension should be based on a formal estimate of abso lute cardiovascular risk and not on an arbitrary blood pressure thresh old. As regards drugs of first choice, the available evidence supports strongly the stance of JNC-V and JNC VI that diuretics and beta-block ers should be preferred unless they are contraindicated, or unless the re are positive indications for other drug classes. (C) 1998 American Journal of Hypertension, Ltd.