Blood pressure lowering for the primary and secondary prevention of stroke: treatment of hypertension reduces the risk of stroke.

Hypertension is the most important risk factor in the development of stroke. It is also the risk factor most amenable to treatment. The results from 18 controlled trials show a reduction in relative risk of stroke of 25-47% among treated hypertensive patients. This reduction applies both to the elderly and to younger patients, but the absolute reductions are greater among the elderly and the number of patients with hypertension that need to be treated to prevent a stroke is lower in the elderly because they have a higher risk of stroke. The reductions in relative but not absolute risk appear to be similar for both isolated systolic hypertension and combined systolic and diastolic hypertension in the elderly. The case for antihypertensive treatment in the secondary prevention of stroke is less clear but the results of four clinical trials of antihypertensive treatment among patients with and without hypertension and a history of cerebrovascular disease point to a probable benefit. The results of the PROGRESS trial will elucidate this further.