THE AUSTRALIAN NATIONAL BLOOD PRESSURE STUDY

Abstract

There is very strong evidence that even a minor degree of hypertension leads to an increased risk of premature death from either stroke or coronary heart disease'. Since the development of antihypertensive drugs 30 years ago, several reports have confirmed that effective treatment of severe hypertension reduces both mortality and the incidence of cardiovascular complications•; the Veterans administration study of patients with diastolic blood pressures between 90 and 114 mm Hg suggested that patients with less severe hypertension might also benefit. This study was comparatively small; the subjects were all men, and the blood pressures had been taken in hospital. There was a high prevalence of pre-existing cardiovascular disease in subjects entering the study. The major question left unanswered by these studies was whether antihypertensive drug treatment would reduce mortality and the prevalence of cardiovascular complications in a population with mild hypertension free of pre-existing hypertensive cardiovascular complications. A second and related question was to what extent failure to treat such individuals would lead to the premature development of deaths and complications of cardiovascular origin. The Australian National Blood Pressure Study• was designed to give answers to both these questions. The study was a placebo controlled therapeutic trial of antihypertensive therapy in 3427 men and women with defined mild hypertension, recruited from the general population by screening. Those with pre-existing cardiovascular disease were excluded.