Blood pressure is one of the key vital signs, and high blood pressure is a risk factor for a number of cardiovascular diseases.
Blood pressure is measured during virtually every medical visit, regardless of the cause or complaint, and is constantly monitored during most hospital care. But which measure is more important? Let’s have a look at Systolic vs. Diastolic.
Blood Pressure Readings
Blood pressure usually consists of two measurements:
Systolic Blood Pressure
Systolic blood pressure is the measure of the maximum amount of pressure that blood circulation puts on the walls of the blood vessels with every beat.
Diastolic Blood Pressure
Diastolic blood pressure is the measure of the minimum amount of pressure on the walls of blood pressure between every beat of the heart.
Normal resting adult blood pressure is 120/80 mmHg, and the global average blood pressure is 127.79 for men and 122/77 for women.
Risks of High Blood Pressure
High blood pressure is called hypertension. Long-term hypertension is a major risk factor for arterial diseases, heart failure and stroke, vision loss, and kidney disease. High blood pressure is generally classified as a resting blood pressure that is consistently over 130/80 or 140/90.
Risks of Low Blood Pressure
Low blood pressure is called hypotension. Consistent low blood pressure may be caused by low blood volume, heart problems, anemia, endocrine problems, and other conditions. Short-term low blood pressure can lead to dizziness or fainting.
Severely low blood pressure can deprive the brain and organs of oxygen and nutrients, putting the body in shock. Systolic pressures below 90 mmHg or diastolic below 60 mmHg are generally considered low blood pressure.
Elevated Systolic Pressure Only
If a person has elevated systolic blood pressure but normal diastolic pressure, the condition is called isolated systolic hypertension. This is the most common form of hypertension in older adults, and is often indicative of arterial stiffness, heart valve problems, obesity or diabetes, or hyperthyroidism.
Isolated systolic hypertension is usually indicated by systolic pressures over 130, and diastolic pressures of 80 or lower.
Lowered Diastolic Pressure Only
When only the diastolic pressure is low, the condition is called isolated diastolic hypotension. Isolated diastolic hypotension is associated with ischemia, and chronic low-level ischemia is associated with elevated risk of heart failure.
Low diastolic pressure can also lead to fainting and falling, which can pose elevated safety risks for seniors. Isolated diastolic hypotension is usually defined by a systolic pressure that is over 100, and a diastolic pressure below 60.
Systolic vs. Diastolic: Which is More Important?
For decades, systolic pressure has received more attention from medical professionals, because it is associated with more urgent medical conditions that require treatment. However, recent years have seen more attention being placed on diastolic pressure.
One unintended side effect of some high blood pressure treatments in older adults is lowering blood pressure down to levels that impact the patient’s quality of life.
The fact remains that high systolic pressure is our current best predictor of cardiovascular disease, particularly among older adults. And yet, systolic pressure alone is not always an accurate indicator of hypertension, and we cannot disregard the risks and challenges of low blood pressure.
Current thinking is that, while systolic pressure is the best indicator of hypertension and precursor to cardiac events, an accurate diagnosis requires a more complete picture of the patient’s entire cardiac health, which means reviewing both systolic and diastolic pressure, and longer-term measurements like 24-hour monitoring.
Studies show that there can be significant differences in blood pressure when taken at home vs. at the office vs. 24 hour ambulatory monitoring, so an accurate diagnosis can’t be based on a single systolic reading … unless that reading is over 180, that is.
Conclusion
The truth is, because blood pressure is so highly variable based on so many factors, there is no single number that is the “most important.” Instead, every individual number in every individual reading needs to be considered to get a comprehensive picture of the patient’s cardiac health.
An elevated systolic blood pressure reading should trigger more careful monitoring of the patient’s blood pressure, with follow up at home, and be the beginning of a longer conversation about heart health and lifestyle choices.
If you had to choose a single blood pressure number to monitor, it would be systolic, since it’s a precursor to so many critical health conditions, and because hypertension is so much more statistically common and deadly. But the better choice is to consider all the values, and have a more comprehensive view of the patient’s cardiac health.