A cost benefit analysis for the treatment and detection of mild hypertens in Australia

Hypertension has long been recognized as a significant health problem in Australia. Since the condition results in reduced life expectancy, and employability, requiring careful monitoring and life long therapy, the choice of treatments requires special care. Mild hypertension is symptomless, and accounts for seventy percent of all cases of hypertension. Most mild hypertensives are unaware of their condition. Chapter one of this dissertation is largely concerned with an outline of the pr~valence and the principal means of detection and treatment of the condition. The cost of lifelong drug therapy, currently the primary means of treatment, is high. A comparison with the alternative non-drug treatments is therefore called for. The aims of this analysis are consistent with guidelines for hypertension control recommended by the National Heart Foundation of Australia. The rest of chapter one, justifies the use of cost-benefit analysis in indicating the desirability or otherwise of government intervention in the market for health care. It is argued that market failure prevents individual decision makers from rationally evaluating the worth of their human capital. Market failure is evident in insurance, lifestyle and through the generation of externalities. The analysis should help to indicate whether a control programme is economically viable, which treatments should be used and who should be treated. Chapter two introduces the taxonomy of benefits and costs used i.e. direct and indirect, visible and invisible savings in morbidity and mortality, which are the major benefits of effective hypertension control. The human capital and willingness to pay approaches for valuation of life are examined. Both approaches can be drawn together when we view insurance and lifestyle as a reflection of individuals willingness to pay, to maintain and increase his own human capital. The permanent ipcome hypothesis can be used to justify valueing pensioners time at the market wage. We must assume that maximising Gross National Product (G.N.P.) does not provide a basis for human capital valuation. Choice of the real discount rate presents some difficulties. Arguments that it ought to reflect the social rate of time preference and the opportunity cost of capital are discussed. The use of the risk-free bond rate is viewed as a reliable proxy. Chapter three examines the benefits (averted costs) of effective control of mild hypertension. A mortality model is developed upon the basis of human capital valuation, yielding the present value of losses for the condition. The stock-flow considerations, largely ignored in other studies are examined. Morbidity costs are categorized by hospitalization, future treatment and loss in labour productivity. An understatement in estimates is likely given the difficulty in quantifying some indirect costs. Chapter four, follows a probabilistic approach in specifying the linkages between diagnosis, treatment and outcome. The costs of treatment consist of screening, drug treatment and the 'salt-modified' diet (non-drug treatment). Sensitivity analysis is performed upon two alternative treatment mixes i.e. diuretic drugs provide the primary course of treatment (the 70% assumption) and non-drug treatment as the initial therapy (the 20% ~ssumption). Chapter five reviews the findings of the cost-benefit analysis. In the aggregate social costs are outweighed by social benefits. A programme based upon salt-diet modification as the primary treatment yields the highest net benefit. Benefit cost ratios suggest that, ideally, the programme should be directed at males aged 65 to 69. Research procedures followed consisted primarily of a review of recent epidemiological studies performed in Australia, the United Kingdom and the United States. Economic analysis, in hypertension research, has been confined largely to costeffective analyses. The increasing sophistication of costeffective analyses and their scope for capturing the nonpecuniary value of saving life, avoiding suffering etc, accounts for the growing usurpation of cost-benefit by cost effective analysis, in health care. More significantly, the use of quality-adjusted life years, as a measure of health output, provides information more readily appreciated by members of the medical profession, generally lacking formal training in economics. The Australian National Blood Pressure Study and the Risk Factor Prevalence Study (National Heart Foundation of Australia 1980) were the primary sources of data. While information on mortality rates is available on an annual basis, very little is available on the incidence of non-fatal events i.e. for stroke and myocardial infarction. Estimates of hypertension related events were inferred. Dissaggregated data on deaths from heart and blood vessel disease, provided by the N.H.F., were received too late to be adequately incorporated. The benefits and efficacy of drug/non drug treatment of mild hypertension remains a contentious issue in epidemiological circles. The forthcoming Medical Research Council Trial (U.K.) should provide more exhaustive information regarding hypertensive related events, and age/sex related benefits of diuretic and beta-blocker therapy, than that currently available. The analysis undertaken is exploratory in nature. The findings largely confirm those views held by the medical profession for the need for concerted efforts at eradicating mild hypertension in Australia. The magnitude of the net benefits are particularly sensitive to choice of adherence-to-therapy probabilities and stock-flow modelling. A more complete analysis is required which incorporates sensitivity to adherence rates, and a purpose built demographic model. A cost-benefit program examining both blood pressure and cholesterol, as the major risk factors in heart,disease would be informative. I wish to thank Bob Rutherford, my supervisor, for assistance provided throughout the preparation of this thesis. Thanks must also go to William Magill, Dr. Trevor Beard (of The Canberra National Blood Pressure Trial) and Stan Crane (of The National Heart Foundation of Australia) for advice and suggestions, (reely given; and to Lyn Kumpulainen the typist.