SYSTOLIC VS. DIASTOLIC BLOOD PRESSURE
As we age, we increase our risk of having a stroke. And high blood pressure is the leading cause of stroke. Thus, it makes sense to regularly monitor our blood pressure. Because we always read it with systolic pressure over diastolic pressure, I asked myself, which of these has more significance in preventing a stroke? Here are excerpts from a recent Harvard Heart Letter by Deepak L. Bhatt, M.D., M.P.H., Which blood pressure number matters most?
Top or Bottom Number—which is more important?
This question comes up often, perhaps because doctors and patients alike tend to pay more attention to the top (first) number, known as systolic pressure. It reflects the amount of pressure inside the arteries as the heart contracts. The bottom (second) number, diastolic pressure, is always lower since it reflects the pressure inside the arteries during the resting phase between heartbeats.
As it turns out, both systolic and diastolic blood pressure are important. Per the most recent guidelines, you have what’s called elevated blood pressure if your systolic blood pressure reading is 120 to 129 mm Hg (which stands for millimeters of mercury). Once your systolic reading reaches 130 or higher or your diastolic reading is 80 or higher, you’re considered to have high blood pressure, or hypertension.
Primary Hypertension
Most people have what’s known as essential or primary hypertension, which means it’s not caused by a medical condition, medication, or substance. Primary hypertension can affect both systolic and diastolic pressure to a similar degree. But sometimes, especially in older people, it affects mainly the systolic pressure; this is called isolated systolic hypertension.
Why does this happen? As you age, your arteries tend to become less elastic and less able to accommodate surges of blood. Blood flowing through your arteries at high pressure can damage the inner lining of these vessels, accelerating the buildup of cholesterol-laden plaque. This further stiffens and narrows the arteries, a condition known as atherosclerosis. Because the same volume of blood has to pass through a smaller area, the systolic pressure tends to rise, while the diastolic pressure remains the same or gradually falls over time. In some people with isolated systolic hypertension, the diastolic pressure reading may drop into the 50s or even the 40s.
Recent Study
Most studies show a greater risk of cardiovascular disease (especially strokes) related to high systolic pressure as opposed to elevated diastolic pressure. But in 2019, an eight-year-long study involving more than 1.3 million adults found that while elevated systolic pressure had a greater effect on cardiac outcomes, high diastolic readings also affected a person’s risk, regardless of the systolic reading.
____________________________________
To help ensure accurate readings when you’re checking your blood pressure, please refer to my April 3, 2021 post Monitor Your Blood Pressure at Home