The PROGRESS Trial: Preventing Strokes by Lowering Blood Pressure in Patients With Cerebral Ischemia

Abstract

A blood pressure is an unhealthy thing to have, to a large extent. Prospective population-based observational studies have shown a continuous, positive relationship between blood pressure and the risk of stroke or other major vascular events. There is no “safe” level of blood pressure below which the risk ceases to diminish. The association is even stronger than one might surmise from casual measurements, because of regression to the mean on subsequent readings. After appropriate correction, prolonged differences in usual diastolic blood pressure of 5, 7.5, and 10 mm Hg are respectively associated with at least 34%, 46%, and 56% relative risk reduction of stroke.1,2 The effectiveness of antihypertensive treatment in the primary prevention of stroke leaves no doubt about the causality of the relationship: systematic reviews show that a diastolic blood pressure reduction of 5 to 6 mm Hg results in a large decrease in stroke rate, in the order of 35% to 50%.3,4 Until now, the question remained whether blood pressure reduction was equally beneficial in patients after a transient ischemic attack (TIA) or a stroke. Theoretically, irreparable damage might already have occurred at the time of the first manifestation of cerebrovascular disease. A slightly crude analogy is that abstaining from cigarettes greatly improves prognosis in the general population but not much in patients with bronchial carcinoma. Systematic reviews showed equivocal benefit of blood pressure reduction in 4 clinical trials in which an episode of brain ischemia was the qualifying event.5 In subsets of patients with previous stroke from trials of antihypertensive treatment in general, the evidence was somewhat more robust, but not for normotensive patients.6 Therefore the recently published PROGRESS trial can be regarded as an impressive undertaking.7 The target population consisted mostly of patients with ischemic stroke, brain TIA, or transient monocular …