Always play it by the numbers with your blood pressure

Managing your blood pressure (BP) is the single most important step you can take to reduce your risk of cardiovascular diseases. And today, we’ll talk a bit about what’s in the numbers.

As a young medical student, I was initially surprised to learn that blood pressure is lower during childhood and slowly rises until adulthood. (And sometimes, it doesn’t stop rising.) I was even more surprised to learn that the standards for BP during various ages in childhood were not clear, at least at that time.

So, during med school, I began researching blood pressure levels in children in the U.S. and in Asia. I tested their levels at rest, and before and after exercise. And I discovered that stress plays a major role in raising blood pressure, even in children. My findings were published in the American Journal of Public Health in 1979.

Doctors have actually been measuring blood pressure since blood pressure cuffs and meters were developed about 100 years ago. This measurement gives the force that flowing blood exerts against the inside walls of blood vessels. Of course, these forces represent mechanical sheering stresses that can cause damage to blood vessel walls. And these stresses are the underlying basis of the hardening and narrowing of the arteries that comprises cardiovascular diseases.

Your blood pressure reading consists of two numbers: systolic and diastolic. The systolic (top number) reading is the high peak of the pressure when your heart beats. The diastolic (bottom number) is the pressure at its low point, in between heartbeats.

Most of us today know that 120/80 is considered “normal” BP. But this wasn’t always so.

During medical school, we were taught that “normal” systolic BP for adulthood was your age plus 100. So, a 60-year-old man was expected to have a systolic BP of 160. And it was essentially okay for a 70-year-old man to have a systolic reading of 170. Experts thought this “asymptomatic” rise of blood pressure with age was “normal.”   And they only recommended drug treatment if your systolic reading rose significantly higher than your age plus 100.

They mistakenly thought high blood pressure due to advancing age was “asymptomatic.” In other words, it didn’t cause any real symptoms. Now we know it’s a silent killer. And it only strikes suddenly with a heart attack, stroke, or aneurysm.

They also mistakenly thought high blood pressure with advancing age was “normal.” And, yes, it was (and is) the “norm” because most modern men and women experience a lifetime of exposure to stress. So their blood pressure rises with age.

But let me be clear…high blood pressure is not “normal.” Far from it.

The reading of 120/80 remains optimal and “lower is even better.” But doctors are now reaching a consensus that 140/90 is the point at which the benefits of using drugs outweigh their risks and side effects in the general population. No matter your age.

But what about the flip side of the blood pressure “coin”?

Low blood pressure is generally a sign of good health as long as the top, systolic pressure is above 80. But anything lower than that can also cause problems. If your blood pressure is too low, it becomes difficult to maintain adequate blood flow against the effects of gravity and other mechanical influences.

A blood pressure drop of 10 to 20 points when you go from lying down or sitting, to a standing position is called “orthostatic hypotension.” You would experience this problem as sudden, passing lightheadedness. This occurrence indicates an inability to regulate blood pressure.

A study in the journal Hypertension followed more than 12,000 adults for 17 years. Those who had episodes of orthostatic hypotension, especially between the ages 45 to 55 years, were more likely to develop heart failure by the end of the study.

Here’s another point to consider: blood pressure measurements should be the same (or very close to it) in both  arms. Research in the medical journal Lancet analyzed 20 studies that measured BP in both arms. They found that a BP difference of 10 to 15 points from one arm to the other increases the risk of dying from heart disease or stroke. A 15-point difference doubled the risk of arterial disease.

These simple blood pressure measurements can tell you a great deal about your health and your risk of cardiovascular diseases. If you have systolic blood pressure readings from 120 to 139, or diastolic readings from 80 to 89, you run a greater risk of developing hypertension. And you should monitor your blood pressure frequently.

If your BP readings stay at 140/90 or above, you need to check with your doctor about starting a treatment program. If you monitor your BP at home and find a reading over 180/110, check it again. If it persists, you should get urgent care to lower it. And be sure to check both arms!


1. “Orthostatic Hypotension as a Risk Factor for Incident Heart Failure The Atherosclerosis Risk in Communities Study,” HypertensionPublished online before print March 19, 2012

2. “Association of a difference in SBP between arms with vascular disease and mortality: a systematic review and meta-analysis,” Lancet 2012; S0140-6736(11)61710-8.