Why are two different numbers used to measure blood pressure?

The first or top number measures the systolic pressure or the pressure that the heart is exerting when it is actually pumping. The bottom number is called the diastolic, and it measures the heart’s pressure between beats or when it is at rest. This means that the top or systolic pressure is the maximum pressure, while the diastolic or bottom number represents the minimum. This will explain why the bottom number is invariably smaller.

Is it true that the bottom number is the most important one?

A. There used to be some feeling that the diastolic reading was more critical than the systolic. However, today most doctors regard both as equally important. In any case both generally move together in the same direction. That is, an increase in one will generally be followed by an increase in the other and vice-versa.

What about the popular saying that a person’s blood pressure should equal 100 plus his age?

In most western countries peoples’ blood pressure does tend to rise until the age of 55 or so. However, there are groups in the South Pacific, South America and Africa whose blood pressure remains the same throughout life. Even in this country, some five per cent of the population retains the same level of blood pressure in old age as they had in youth. The fact that blood pressure usually does go up with age does not mean it must or should go up. Dr. Josef R Hrachovec, a research physician at the Gerontology Centre at the University of Southern California says in his book, Keeping Young and Living Longer, that “low blood pressure throughout life is truly and perfectly normal.” It’s also most desirable and, in many cases, perfectly attainable.

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