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How To Interpret Blood Pressure

The way your doctor interprets your blood pressure reading could make a big difference in your health. CBS medical correspondent Dr. Emily Senay tells us why.

The way that blood pressure readings should be interpreted has changed. But a survey of doctors out this morning shows that many do not know about the changes.

Just about everybody has had their blood pressure taken at one time or another. It's a standard vital sign that doctors use to tell if there's a health problem.

What the doctor is listening for with his stethoscope after he inflates the armband is the sound of blood flowing through the arteries as the armband is slowly released. Those sounds translate into a blood pressure reading.

The reading tells us how elastic our blood vessels are. As we age, blood vessels become more and more resistant to blood flow. The more resistant, the higher the blood pressure. Most of us know that there are two numbers that make up a blood pressure reading.

The normal blood pressure reading is 120 over 80. The top number is the systolic reading and the bottom number is the diastolic reading.

In the recent past doctors were more concerned when the lower number was too high. But now new studies show that both numbers are very important and that the higher number may be even more important when it comes to contributing to heart attacks and strokes.

Q: If the top number has been found to be so important, why don't doctors know about it?

A: Sometimes it's very difficult to get doctors to change their practices when the conventional wisdom is so entrenched.

Q: How serious is this problem?

A: High blood pressure contributes to heart attacks, strokes, and kidney problems, and those are just a few of the consequences if left untreated.

About 50 million Americans have high blood pressure. Despite this new information it's estimated only half are being treated. And only 30% are treated adequately.

Q: Until now, why was the lower number considered more important?

A: One reason is that early research into high blood pressure focused mainly on the lower number, and didn't look too hard at anything else. The second reason is that it's normal for blood pressure to rise as people age, so a raised upper number of 160 over 80 was thought to be okay. But with these new studies, we now know that an upper number of 160 is dangerously high.

Q: How often should you have your blood pressure taken?

A: Depends on your age and your medical history, etc.

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