ArticlesRisks of untreated and treated isolated systolic hypertension in the elderly: meta-analysis of outcome trials
Introduction
The prevalence of isolated systolic hypertension rises curvilinearly with age, averaging 8% in sexagenarians and exceeding 25% beyond 80 years.1 Isolated systolic hypertension is a distinct pathophysiological entity, in which the rise in systolic blood pressure is mainly due to a decreased elasticity of the large arteries and is not necessaily accompanied by a rise in maen arterial blood pressure or in preipheral resistance.1
Among the cardiovascular risk factors amenable to prevention in the elderly, systolic hypertension is of major importance.1 The past decade witnessed the publication of three outcome trials,2, 3, 4 which specifically addressed the question whether in the elderly the cardiovascular risk conferred by isolated systolic hypertension is reversible by antihypertensive drug treatment. Earlier published trials also included groups of older patients with isolated systolic hypertension.5, 6, 7, 8, 9 Previous meta-analyses of outcome trials in hypertension10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21 did not provide specific estimates of the risks in treated and untreated older patients with isolated systolic hypertension or explained treatment benefit mainly in function of the achieved diastolic blood pressure. We therefore reanalysed the evidence from the published trials. In untreated control patients we first evaluated the risk conferred by systolic and diastolic blood pressure at baseline both before and after correction for regression dilution bias.22, 23 We then calculated pooled estimates of relative and absolute benefit of antihypertensive drug treatment with and without stratification for the risk at baseline.
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Acquisition and selection
We defined isolated systolic hypertension as it was in two published trials.3, 4 Systolic blood pressure below 95 mm Hg. As in other studies,2, 5 we set the lower boundary of old age at 60 years without an upper limit. We screened published overviews10, 13, 16, 21 and reports on collaborations between trialists14, 15 for outcome studies in hypertension, in which older patients with isolated systolic hypertension had been enrolled. Among the trials with eligible patients, we excluded seven: the
Characteristics of trials
The main characteristics of the trials appear in table 1. In SHEP, Syst-Eur, Syst-China, EWPHE, and MRC1, the stratification criteria included centre,2, 3, 4, 9 sex,3, 4, 5, 9 age,9 previous cardiovascular complications,3, 4, 5 or anti-hypertensive drug treatment at initial contact.2 No stratification was applied in HEP, STOP, and MRC2. The SHEP, Syst-Eur, EWPHE, HEP, and STOP trials relied on balanced randomisation to active medication or a control group. In MRC1 and MRC2 the patients were
Discussion
Previous meta-analyses focused on the role of diastolic blood pressure as cardiovascular risk factor17, 22, 31 and studied the benefit of antihypertensive drug treatment relative to the achieved reduction in diastolic blood pressure.10, 19 In our overview we found that in untreated patients systolic blood pressure was a more accurate predictor of mortality and cardiovascular complications than diastolic blood pressure. After correction for regression dilution bias,22, 23 a 10 mm Hg increase in
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