The evolution of antihypertensive therapy

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  • Sm. Sci. Med. Vol. 31, No. II. pp. 1239-1243, 1990 Printed in Great Britain

    0277-9536/90 S3.00+0.00 Pergamon Press plc

    THE EVOLUTION OF ANTIHYPERTENSIVE THERAPY

    ICHIRO KAWACHI and NICHOLAS WILSON~ Department of Community Health, Wellington School of Medicine, P.O. Box 7343, Wellington, New

    Zealand and *National Health Institute, Department of Health, Wellington, New Zealand

    Abstract-The goal of antihypertensive therapy has changed dramatically over the past 40 years. What was once a treatment for a life-threatening disease has gradually evolved to become just one of the many ways of modifying a symptomless risk factor. The development of safer drugs throughout the 1970s resulted in treatment being offered at successively lower levels of blood pressure elevation, and consequently to an ever increasing proportion of the population. Based on new evidence from clinical trials, however, recent policy guidelines for the treatment of hypertension-especially mild hypertension- have become more conservative. Yet, there are a number of reasons for doubting that this policy reversal will LX transmitted into actual clinical practice, unless major changes are made to the arrangement of structural interests-professional, industrial and third-party funders-which currently support and maintain antihypertensive therapy on a mass scale. Meanwhile, control of blood pressure, quality of life, and compliance with therapy have become ends in themselves, often to the exclusion of much-needed discussion on the real therapeutic goal of antihypertensive medication, i.e. the prevention of cardiovascular and cerebrovascular morbidity and mortality and the question of whether drugs are always the best way to achieve this.

    Key words-hypertension, antihypertensive drug therapy, health policy

    INTRODUCTION

    The nature and rationale of antihypertensive drug treatment have changed dramatically over the past four decades. The first antihypertensive drugs were introduced in the 1950s for the treatment of malig- nant hypertension, a symptomatic disease, potentially lethal if left untreated [l]. The successful treatment of malignant hypertension was followed in the 1960s by randomized trials demonstrating the value of phar- macological therapy for severe hypertension [2,3].

    Since then, we have witnessed a progressive lower- ing of the cutoff level of blood pressure for treatment, until hypertension has become what it is today-no longer a disease, but a cardiovascular risk factor- and lowering the blood pressure with drugs can no longer be regarded as a treatment (as it used to be for malignant hypertension), but is in fact a form of prevention [4,5]. The development of safe and effec- tive drugs has led to a gradual shift in the locus of treatment away from the hospital and into the com- munity, where much of preventive activity takes place today. The advent of safer drugs has also tipped the balance between the risks and benefits in favour of offering treatment to asymptomatic people, so that we have witnessed a progressive redefinition of need in terms of lower levels of blood pressure requiring treatment.

    Over the last 4 years however, there has been an accumulation of new evidence from clinical trials about the benefits of treating mild to moderate hypertension [6]. This has prompted fresh debate about the wisdom of treating large numbers of indi- viduals in the population with mild to moderate elevations of blood pressure [7,8], and resulted in more conservative guidelines for pharmacological treatment [g-12]. While these guidelines suggest a retrenchment of opinion at the policy-making level,

    there are a number of reasons to doubt that estab- lished clinical practice will be influenced swiftly or significantly. In this paper, we analyse the history of hypertension from the viewpoint of the major interest groups and their interactions which have shaped the diffusion and evolution of drug treatment as it is practised today.

    THE EVOLUTION OF ANTIHYPERTENSIVE THERAPY-THE ROLE OF THE

    MEDICAL PROFESSION

    The risks associated with raised blood pressure were recognized as far back as in 1925. Data from the Actuarial Society of America demonstrated a con- tinuous rise in mortality associated with stepwise increases in blood pressure in an insured population [13]. Knowledge of the risks of raised blood pressure preceded the availability of hypotensive drugs, which were introduced for the first time in the 1950s. Their efficacy in reversing the effects of malignant hyperten- sion were so convincing that randomized trials were felt to be unnecessary [9].

    Once a new therapy has achieved success in one group of patients, there is an inevitable tendency to use it with other patients [14]described by McKinlay [15] as the process of professional adop- tion in his analysis of the diffusion of medical technology. Encouraged by the promising reports of the pharmacological reversal of malignant hyperten- sion, it was natural for clinicians to wonder if similar success might be obtained by treating people with blood pressures at levels lower than in malignant hypertension. After all, studies of the natural history of raised blood pressure, including the Framingham Heart Study [16], had shown that the risk of death rose steadily from the lowest to the highest levels of blood pressure. Reflecting on the implications of their

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  • 1240 ICHIRO KAWACHI and NICHOLAS Wnso~

    study, the Framingham investigators wrote in 1972: The usual medical practice focuses on the treatment of ill people, (however) the prevention of cardiovas- cular diseases may actually require the evolution of a new breed of physicians. . . Such practitioners must come to regard the occurrence of stroke, coronary heart disease, congestive heart failure and peripheral vascular disease. . . as a medical failure rather than the starting point of medical treatment (17, empha- sis in the original]. The evolution alluded to by these authors signalled the beginning of the process of widespread professional adoption and diffusion of drug treatment for hypertension. In 1972 the National Heart and Blood Pressure Education Pro- gramme launched a large-scale campaign to educate the American public about the risks of hypertension. Successive policy guidelines issued throughout the 1970-80s by this authoritative policy-making body led to the gradual lowering of the cutoff level of blood pressure recommended for drug treatment [18].

    A new breed of physicians were urged to extend their treatment to people with lesser degrees of blood pressure elevation, who were essentially asymp- tomatic. Strokes and heart attacks were to be re- garded as medical failures; an attitude that betrays the discomfort that many clinicians feel in merely observing people at risk of developing disease, and which turned into one of the potent forces fuelling the process of professional adoption [4].

    By 1980, the stage of professional adoption was virtually complete, and the pharmacological treat- ment of hypertension, even at the lowest levels of elevation, had attained the status of a standard procedure. The Joint National Committee report, published in that year (191 recommended that all patients with diastolic blood pressures above 90 mmHg ought to be treated, even in uncompli- cated cases. Defined in this way, nearly 20-30% of the population in many Western countries now had levels of blood pressure requiring drug treatment [20].

    The treatment of hypertension did not, however, attain the status of standard procedure without controversy. Sir George Pickering was one eminent authority who repeatedly deplored the arbitrary di- chotomization of normal blood pressure and hyper- tension, insisting instead that the differences are quantitative rather than qualitative [21]. The medical profession speak of hypertension as if at some point in the continuous distribution of blood pressure in the population, the risk of cardiovascular disease suddenly jumps, whereas epidemiological data have repeatedly demonstrated that the distribution of blood pressures within populations is unimodal, and that the relationship between blood pressure and the risk of complications is curvilinear [22]. Pickering felt that this transformation of quantity into quality was an indication of the inability of the medical pro- fession to conceive of patient characteristics in terms other than either/or, diseased/not diseased [21]. As it turns out, this conception of an arbitrarily defined level of blood pressure as diseased has led to the successive redefinition of the level of blood pressure needing treatment, as well as to far-reaching conse- quences for the labelling of large sections of the population, the creation of demand for medical treatment and for the supply of drugs to treat it.

    Randomized clinical trials of antihypertensive therapy were being conducted throughout the process of diffusion. However it is evident in retrospect that wide-ranging recommendations for treatment were often issued too early and with too much alacrity. It can be argued for instance that the recommendations of the Joint National Committee over the past 10 years have on occasions been based upon inadequate or inappropriate evidence. Their report in 1977 [23] which recommended the treatment of people with diastolic blood pressures above 105 mmHg (and the individualization of treatment for pressures between 90 and 104mmHg), was based upon the one single clinical trial which had been reported at that time, the Veterans Administration Cooperative Trial [24]. Yet the same trial was rejected from a recent meta- analysis of all the published trials in existence, on the grounds that the patients in it were hospitalized men, and consequently did not reflect the community management of hypertension [25]. Similarly, the 1980 report