A medical study from Wake Forest Baptist Medical Center published an article in the journal, Internal Medicine, in June of 2014 that contradicts common medical belief that when treating hypertension, the lower the better. They studied 4,480 patients for 21 years and found that once blood pressure is below 140, there is no benefit in loweing the systolic (higher number) below 140 mm of mercury. The benefits that were assessed included angina, congestive heart failure, ischemic (blood clots vs hemorrhage) stroke, and death.
We also have to keep in mind that tissue perfusion is what is involved when we have a stroke and that this can happen with both high and low blood pressure. High blood pressure creates blockages in arteries that restrict blood flow, and low blood pressure can lower perfusion considerably if a blood vessel has a blockage to start with.