Prevalence of hypertension in Kimberley Aborigines and its relationship to ischaemic heart disease: An age-stratified random survey

Objective: To determine the age-specific prevalence of systolic and diastolic hypertension and of electrocardiographic abnormalities in the Aboriginal population of the Kimberley region of Western Australia. Design and setting: Age and sex stratified random samples of the Aboriginal population of the Kimberley region were selected and located. Measurements were made of systolic and diastolic blood pressure and electrocardiograms (ECG) were recorded. Hypertension was defined as a systolic blood pressure of 160mmHg or greater or diastolic blood pressure of 95mmHg or greater. ECG abnormalities were classified by the Minnesota system. Participants: Measurements were made on 249 men and 241 women distributed in seven age bands above 15 years and representing 78% of the selected men and 76% of the selected women. Interventions: In addition to ECG and blood pressure, measurements were made of height and weight and information was obtained on medication, smoking, drinking and diet. A sample of venous blood was obtained. Main outcome measures: The data obtained on blood pressure, hypertension and ECG abnormalities were compared with existing data on Caucasian and Aboriginal Australians. Results: Aboriginal men below the age of 30 years showed particularly high blood pressure compared with Caucasian men. The overall prevalence of hypertension in Aboriginal men 50 years of age and older was 45%. The prevalence of hypertension among Aboriginal women increased sharply from 35 years of age with a maximum between 55 and 65 years. The overall prevalence of hypertension in women 50 years of age and older was 50%. By regression, the average systolic/diastolic blood pressure at 40 years was 137/85mmHg for men and 135/83mmHg for women. ECG abnormalities indicating ischaemic heart disease (IHD) were more prevalent in both male and female Aborigines than had been found for Caucasians in 1966. In both sexes IHD and especially code 1.1 indicating myocardial infarct were associated with systolic hypertension. Conclusions: The prevalence of both systolic and diastolic hypertension and of probable IHD was two to three times higher in Kimberley Aborigines than in Caucasian Australians. ECG evidence of infarct was significantly related to systolic hypertension in both sexes.