Diastrolic vs. Systolic Blood Pressure: Which is Most Important?

When a doctor takes your blood pressure, they give you two readings. The first reading is a measure of the systolic blood pressure and the other is the diastolic pressure. Both numbers are important - but which should you be most concerned about? Diastolic vs. systolic blood pressure - here's what you need to know about each.

Diastolic vs. Systolic Blood Pressure: What's the Difference?

When a doctor tells you your blood pressure is 120/80 mm Hg, the upper number (120 mm Hg) is the systolic blood pressure. This is the maximal pressure in the arteries at the moment the heart contracts or beats. The lower number (80 mm Hg) is a measure of the lowest pressure in the arteries when the heart relaxes between contractions. It's possible for one of these readings to be abnormal and the other to be completely within range. So which one is most likely to cause heart disease, stroke or other health problems if it's out of range?

It depends on your age. According to a recent study published in the Journal of General Internal Medicine, if you're under the age of 50 a high diastolic blood pressure is a better predictor of early mortality than an elevated systolic blood pressure. The opposite is true if you're over the age of 50 when a high systolic pressure becomes the best predictor of early death.

This doesn't mean that if you're over the age of 50 a high diastolic blood pressure isn't important anymore - it is. It too increases the risk of dying early, but it's not the best predictor of future health problems and death.

High Systolic Pressure is Common in Older People

High systolic blood pressure becomes more common with age. In fact, two-thirds of people over age 60 have a systolic blood pressure that's too high. Unfortunately, doctors are less likely to treat high systolic pressures than they are diastolic ones, which can put older people at greater risk for dying of heart disease or stroke. High systolic blood pressures become a problem as the arteries stiffen with age, which increases the workload on the heart.

Diastolic vs. Systolic Blood Pressure: The Bottom Line?

Anyone who has a systolic blood pressure greater than or equal to 140 mm Hg. or a diastolic pressure of 90 mm Hg. or more needs to get bring down to reduce their risk of premature death. Talk to your doctor about the best way to do this.

References:

Medscape.com. "Systolic Blood Pressure Elevation in Elderly Persons"

Journal of General Internal Medicine. "Impact of Diastolic and Systolic Blood Pressure on Mortality: Implications for the Definition of Normal"

Eurekalert.org. "Redefining Normal Blood Pressure"