Hypertension and the risk of ischaemic heart disease.

The magnitude of the effect of hypertension as a risk factor for acute myocardial infarction (AMI) was estimated in 250 patients who presented with a first AMI who were aged 35-64 years (199 survivals and 51 deaths within 24 h), whose names were obtained from a community-based register of myocardial infarctions in the Hunter Region of New South Wales. The cases were matched by sex, age and residential area, and control subjects were obtained from a random population sample from the same region. A history of hypertension (odds ratio, 5.5; 95% confidence limits, 3.4 and 8.9) and treatment for hypertension (odds ratio, 4.2; 95% confidence limits, 2.5 and 7.2) were each significantly (P less than 0.0001) associated with an increased risk of AMI--persons with treated or untreated hypertension were four to five times more likely to develop AMI than were persons without hypertension. Adjustment for smoking did not affect the association between hypertension and the incidence of AMI. Cigarette smoking appears to have had less influence on the incidence of AMI (odds ratio, 1.7; 95% confidence limits, 1.1 and 2.4; P less than 0.01) than did a history of hypertension. Twenty-four per cent of the first AMIs that occurred in the study population were attributable to hypertension (after adjustment for smoking) and twenty-seven per cent were attributable to smoking (after adjustment for hypertension).