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The possibility that hypokalaemia might increase the mortality of treated hypertensives in the Glasgow Blood Pressure Clinic has been examined by comparison of serum potassium in decedents and survivors and by calculation of age-adjusted mortality rates for patients grouped in quartiles of serum potassium measured at the last clinic visit. In this study, 3783 patients with non-malignant hypertension were followed for an average of 6.5 years and of these 1907 had one or more measurements of serum potassium during their last year of attendance. Serum potassium fell in 414 patients given diuretics with or without other drugs except beta-blockers. This fall was similar in those who died of ischaemic heart disease (3.71 mmol/l) and in those who survived (3.72 mmol/l). Serum potassium rose in 167 patients who received beta-blockers with or without other drugs except diuretics and fell slightly among 1326 patients taking other combinations of drugs. There were no significant differences in serum potassium between decedents and survivors in either of these treatment groups. Age-adjusted mortality in deaths per 1000 patient-years in the lowest quartile of serum potassium (less than 3.7 mmol/l) was 28.1 for men and 15.0 for women. Higher serum potassium was associated with slightly, but not significantly, higher mortality in both sexes. There was no relation between serum potassium and mortality in patients with left ventricular hypertrophy, nor was there a relation when death due to ischaemic heart disease was considered separately. Failure of hypokalaemia to predict outcome was confirmed by univariate and multivariate analyses which included, in addition to potassium, assessment of cigarette smoking, initial blood urea and electrocardiographic findings.(ABSTRACT TRUNCATED AT 250 WORDS)

The mortality of 3783 non-malignant hypertensive patients attending the Glasgow Blood Pressure Clinic between 1968 and 1983 and followed for an average of 6.5 years was compared with that in three control groups: the general population of Strathclyde a group of 15 422 subjects aged 45-64 years and screened in Renfrew and Paisley between 1972 and 1976, and a group of hypertensives seen in a blood pressure clinic based on general practice in Renfrew. Average blood pressure for men at entry to the Glasgow Clinic was 181/111 mmHg falling to 158/96 mmHg during treatment. Corresponding values for women were 185/109 mmHg and 161/96 mmHg. Seven hundred and fifty clinic patients (451 males) died during follow-up, the commonest causes of death in both sexes being myocardial infarction and stroke. All-cause age-adjusted mortality (deaths per 1000 patient-years) was 41.4 for men and 22.1 for women. At all ages in both sexes and for all levels of initial blood pressure mortality was less in patients whose blood pressure was reduced most. Without a randomized control group it is not certain that lower mortality in those with well controlled blood pressure was due to treatment, although this is the most likely explanation. Cigarette smoking, a history of myocardial infarction, angina or stroke, retinal arterio-venous nipping, raised blood urea, an abnormal electrocardiogram (ECG) and secondary hypertension were associated with increased risk, but heavy alcohol intake, obesity, haematocrit greater than 45%, hypokalaemia and social class were not. Life table analysis showed that, despite some reduction of mortality by treatment, the relative risk to men and women in the clinic remained two- to five-times that of the general population. The benefits of treatment were not such as to restore normal expectation of life even when blood pressure was well controlled. Excess mortality in the clinic could not be explained by difference of smoking habit or social class. This suggests that there is in the hypertensive patients of the Glasgow Clinic an element of irreducible risk, that treatment may be beneficial in some respects but harmful in others, or that patients at particularly high risk are selectively referred to the clinic.