Primary and secondary prevention of stroke.

Data from prospective observational studies indicate that usual levels of blood pressure are directly and continuously related to the risk of stroke. a prolonged difference in usual diastolic blood pressure levels of just 5 mmHg would eventually confer about a one-third difference in stroke risk, with similar proportional effects in hypertensives and non-hypertensives. The results of randomised trials of blood pressure lowering drugs in hypertensive patients suggest that much or all of this long-term potential stroke avoidance can be achieved within just a few years of beginning treatment. Overall in 17 randomised trials of antihypertensive treatment, a net blood pressure reduction of 10-12 mmHg systolic and 5-6 mmHg diastolic, conferred a reduction in stroke incidence of 38% SD 4, with similar reductions in fatal and non-fatal stroke. Additionally, the sizes of the reductions were similar in trials in mild, moderate or more severe hypertension, in trials in older or younger patients and in trials in patients with or without a history of cerebrovascular disease. Because the proportional effects of treatment were similar in all these groups, the absolute effects of treatment on stroke varied in direct proportion to the background risk of stroke. The greatest benefits were, therefore, observed among those with a history of cerebrovascular disease, those above the age of 60 years, and those with more severe hypertension.