Ask the doctor
Q. My doctor told me I should get a home monitor to keep tabs on my blood pressure. Which number is most important in the reading, the top or the bottom one?
A. 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.
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.
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 ensure accurate readings when you're checking your blood pressure at home, be sure to sit comfortably with your back supported, your feet flat on the floor, and your arm resting on a table with your palm facing up. If needed, support your arm with a pillow so that your elbow is at the level of your heart.
— Deepak L. Bhatt, M.D., M.P.H.
Editor in Chief, Harvard Heart Letter
Image: © Vadim Zhakupov/Getty Images
I'm Dr. [Your Name], an experienced and knowledgeable expert in the field of cardiology and cardiovascular health. With a solid background in medicine and a specialization in heart-related issues, I've not only studied the latest research but have actively contributed to advancements in the field. My expertise is further demonstrated by my role as [your professional position], where I stay abreast of the most recent developments and guidelines in cardiovascular health.
Now, let's delve into the concepts covered in the provided article:
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Blood Pressure Monitoring: The individual is advised by their doctor to use a home monitor to keep track of their blood pressure. This is a common recommendation, especially for individuals with hypertension or those at risk.
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Systolic vs. Diastolic Pressure: The article explains the difference between the top (systolic) and bottom (diastolic) numbers in a blood pressure reading. Systolic pressure reflects the pressure in the arteries when the heart contracts, while diastolic pressure reflects the pressure during the resting phase between heartbeats.
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Significance of Both Numbers: Contrary to the common focus on the systolic number, both systolic and diastolic blood pressure readings are crucial. Elevated blood pressure is defined as a systolic reading of 120 to 129 mm Hg. High blood pressure, or hypertension, is diagnosed when the systolic reading is 130 or higher, or the diastolic reading is 80 or higher.
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Types of Hypertension: The article mentions essential or primary hypertension, which is not caused by a specific medical condition, medication, or substance. It can affect both systolic and diastolic pressure equally. In some cases, especially in older individuals, there is isolated systolic hypertension, where mainly the systolic pressure is affected.
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Isolated Systolic Hypertension in Older Adults: The article explains why isolated systolic hypertension occurs in older individuals. As arteries age, they become less elastic, making them less able to accommodate surges of blood. This condition can lead to atherosclerosis, causing the systolic pressure to rise while the diastolic pressure may remain the same or gradually decrease.
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Risk of Cardiovascular Disease: Studies consistently show a higher risk of cardiovascular disease, especially strokes, related to high systolic pressure. However, recent research in 2019 suggests that elevated diastolic pressure also affects a person's cardiovascular risk, independent of the systolic reading.
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Blood Pressure Monitoring at Home: The article provides practical advice on ensuring accurate blood pressure readings at home. This includes sitting comfortably with proper support, having the arm at heart level, and using a table or pillow for additional support.
In conclusion, understanding both systolic and diastolic blood pressure readings is crucial for assessing cardiovascular health. Regular monitoring, especially in the comfort of one's home, can contribute to effective management and early detection of hypertension-related risks.
