Reliable assessment of the effects of treatment on mortality and major morbidity, II: observational studies

Randomised trial of a perindopril-based blood-pressure-lowering regimen among 6,105 individuals with previous stroke or transient ischaemic attack

BACKGROUND

Blood pressure is a determinant of the risk of stroke among both hypertensive and non-hypertensive individuals with cerebrovascular disease. However, there is uncertainty about the efficacy and safety of blood-pressure-lowering treatments for many such patients. The perindopril protection against recurrent stroke study (PROGRESS) was designed to determine the effects of a blood-pressure-lowering regimen in hypertensive and non-hypertensive patients with a history of stroke or transient ischaemic attack.

METHODS

6105 individuals from 172 centres in Asia, Australasia, and Europe were randomly assigned active treatment (n=3051) or placebo (n=3054). Active treatment comprised a flexible regimen based on the angiotensin- converting-enzyme inhibitor perindopril (4 mg daily), with the addition of the diuretic indapamide at the discretion of treating physicians. The primary outcome was total stroke (fatal or non-fatal). Analysis was by intention to treat.

FINDINGS

Over 4 years of follow up, active treatment reduced blood pressure by 9/4 mm Hg. 307 (10%) individuals assigned active treatment suffered a stroke, compared with 420 (14%) assigned placebo (relative risk reduction 28% [95% CI 17-38], p<0.0001). Active treatment also reduced the risk of total major vascular events (26% [16-34]). There were similar reductions in the risk of stroke in hypertensive and non-hypertensive subgroups (all p<0.01). Combination therapy with perindopril plus indapamide reduced blood pressure by 12/5 mm Hg and stroke risk by 43% (30-54). Single-drug therapy reduced blood pressure by 5/3 mm Hg and produced no discernable reduction in the risk of stroke.

INTERPRETATION

This blood-pressure-lowering regimen reduced the risk of stroke among both hypertensive and non-hypertensive individuals with a history of stroke or transient ischaemic attack. Combination therapy with perindopril and indapamide produced larger blood pressure reductions and larger risk reductions than did single drug therapy with perindopril alone. Treatment with these two agents should now be considered routinely for patients with a history of stroke or transient ischaemic attack, irrespective of their blood pressure.

The INSIGHT and NORDIL trials: Are calcium antagonists equivalent to established drug therapies for cardiovascular protection?

Calcium channel blockers have come into worldwide use for treating hypertension and other circulatory disorders. In recent years, results of several observational studies have suggested that these drugs may not be as safe or effective as other available therapies, such as diuretics and beta-blockers, in the prevention of cardiovascular events. The Nordic Diltiazem (NORDIL) and the International Nifedipine GITS Study: Intervention as a Goal in Hypertension Treatment (INSIGHT) studies were the first two randomized interventional trials in hypertensive patients that directly compared the effects of therapy based on calcium antagonists with those of diuretic and beta-blocker-based treatment on major cardiovascular endpoints. Both studies found that the effectiveness of calcium antagonist therapy was similar to that of diuretic and beta-blocker therapy for preventing the composite primary endpoint of fatal and nonfatal stroke, myocardial infarction, and other cardiovascular death. The two studies shared several nonsignificant trends for cause-specific events, including greater stroke prevention and lesser coronary event prevention in the calcium antagonist groups compared with the diuretic and beta-blocker groups. There is not yet sufficient evidence to prove whether cause-specific differences exist. Results of the NORDIL and INSIGHT studies support incorporating calcium antagonist-based therapy as an additional safe and effective approach for preventing blood pressure-related illness and death.

Prospectively designed overviews of recent trials comparing antihypertensive regimens based on different drug classes

Randomized trials have provided clear evidence of the beneficial effects of many different blood pressure-lowering regimens compared with placebo. The comparative effects of antihypertensive regimens based on different drug classes are less well established. The Blood Pressure Lowering Treatment Trialists' Collaboration conducted a series of prospectively designed overviews of randomized trials that compared the effects of different drug classes on major cause-specific outcomes. These overviews found no differences between the effects of regimens based on angiotensin converting enzyme inhibitors and those based on diuretics or b-blockers. There was limited evidence of small differences between regimens based on calcium antagonists and those based on diuretics or beta-blockers. The overviews of regimens based on calcium antagonists compared with those based on angiotensin converting enzyme inhibitors recorded too few events to provide reliable findings. Over the next few years, the findings of ongoing trials and future cycles of overview analyses conducted by the Collaboration should substantially add to these data.

Effect of pravastatin on frequency of fracture in the LIPID study: secondary analysis of a randomised controlled trial. Long-term Intervention with Pravastatin in Ischaemic Disease

BACKGROUND

Statins inhibit the same biochemical pathway as aminobisphosphonates, therefore these cholesterol-lowering agents may have a beneficial effect on osteoporosis. This possibility has been supported by the finding that some statins also stimulate bone formation, and by observational studies suggesting that patients using statins have higher bone densities and lower fracture rates than controls. To assess whether statins have clinically significant effects on bone, we studied the frequency of fractures in a large randomised controlled trial of these agents.

METHODS

9014 patients (17% women, median age 62 years) with ischaemic heart disease were randomly assigned pravastatin 40 mg daily or placebo and followed up for a mean of 6.0 years. Fractures were ascertained from adverse-event reports.

FINDINGS

101 patients in the placebo group were admitted to hospital for fracture compared with 107 in the pravastatin group (hazard ratio 1.05 [95% CI 0.80-1.37]). When patients with fractures not necessitating hospital admission were added, the total number of patients having a fracture was 183 in the placebo group and 175 in the pravastatin group (0.94 [0.77-1.16]). Separate analyses for women alone and for individuals aged 65 years and over gave similar results.

INTERPRETATION

These findings offer no support for the hypothesis that statins have a significant effect on fracture risk. However, this study was not of an osteoporotic population, and fracture rate, although clinically important, is an insensitive index of effects on bone. Statins should not be used to prevent osteoporosis until there is evidence for their efficacy based on randomised controlled trials.

Reliable assessment of the effects of treatment on mortality and major morbidity, I: clinical trials

This two-part review is intended principally for practising clinicians who want to know why some types of evidence about the effects of treatment on survival, and on other major aspects of chronic disease outcome, are much more reliable than others. Although there are a few striking examples of treatments for serious disease which really do work extremely well, most claims for big improvements turn out to be evanescent. Unrealistic expectations about the chances of discovering large treatment effects could misleadingly suggest that evidence from small randomised trials or from non-randomised studies will suffice. By contrast, the reliable assessment of any more moderate effects of treatment on major outcomes--which are usually all that can realistically be expected from most treatments for most common serious conditions--requires studies that guarantee both strict control of bias (which, in general, requires proper randomisation and appropriate analysis, with no unduly data-dependent emphasis on specific parts of the overall evidence) and strict control of random error (which, in general, requires large numbers of deaths or of some other relevant outcome). Past failures to produce such evidence, and to interpret it appropriately, have already led to many premature deaths and much unnecessary suffering.