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Mortality in patients of the Glasgow Blood Pressure Clinic
Insights
Hypertension treatment in the Glasgow Blood Pressure Clinic reduced mortality, but patients still faced a 2-5 times higher risk than the general population. Even well-controlled blood pressure did not restore normal life expectancy.
Area of Science:
- Cardiovascular Medicine
- Public Health
- Epidemiology
Background:
- Hypertension is a significant public health concern associated with increased mortality.
- Effective management of high blood pressure is crucial for improving patient outcomes.
Purpose of the Study:
- To evaluate the long-term mortality of non-malignant hypertensive patients treated at the Glasgow Blood Pressure Clinic.
- To compare mortality rates with general population and general practice-based hypertensive cohorts.
- To identify risk factors associated with mortality in hypertensive patients.
Main Methods:
- Retrospective cohort study of 3783 hypertensive patients (1968-1983) with an average 6.5-year follow-up.
- Comparison with three control groups: general population, screened subjects (45-64 years), and general practice hypertensives.
- Analysis of all-cause mortality, causes of death, and association with various risk factors.
Main Results:
- All-cause age-adjusted mortality was 41.4/1000 patient-years for men and 22.1/1000 for women.
- Myocardial infarction and stroke were the most common causes of death.
- Mortality decreased with greater blood pressure reduction, but relative risk remained 2-5 times higher than the general population.
- Risk factors included smoking, prior cardiovascular events, raised blood urea, abnormal ECG, and secondary hypertension.
Conclusions:
- While treatment reduced mortality, hypertensive patients in the clinic had persistently elevated mortality risk.
- Normal life expectancy was not achieved even with well-controlled blood pressure.
- Irreducible risk factors, potential treatment harms, or selective referral of high-risk patients may explain excess mortality.
Abstract:
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.