Do you know your blood pressure? A new study from the University of Michigan gives more reason to control blood pressure. High blood pressure is known to increase risk of a stroke, but this study shows the cumulative effect of years of high blood pressure further increases the risk. Systolic, the top number of a blood pressure reading, shows how hard the heart is working to move blood through the arteries. Researchers wrote in JAMA Network Open that having systolic readings ten points higher than average may raise overall stroke risk twenty percent and risk of ischemic stroke by more than thirty percent. They say early diagnosis of high blood pressure and sustained control over a lifetime are critical to preventing strokes.