High blood pressure is common and often uncontrolled, especially in elderly women, a new study shows.

As people age, they are more likely to have high blood pressure and less likely to control the problem, states a report in The Journal of the American Medical Association.

Dangerous Condition

High blood pressure raises the odds of heart attack and stroke, among other health problems.

The new study showed that. Heart attacks, strokes, hospitalization for heart failure, or other fatal heart problems were much more common among people older than 80 with above-normal blood pressure.

About one in three American adults has high blood pressure, but nearly a third of them don't know it, states the American Heart Association's web site.

A quick test can check blood pressure. Lifestyle changes (such as a healthy diet, stress control, and exercise) can help. Many patients may also need medication to tame their blood pressure.

As America ages, high blood pressure may become even more widespread, write the researchers. They included Donald Lloyd-Jones, MD, ScM, of the preventive medicine department at Northwestern University's medical school in Chicago.

Read WebMD's "High Blood Pressure: The Invisible Risk"

What Is High Blood Pressure?

Curious about where you stand? Here's a quick guide.

-- High blood pressure: Systolic blood pressure (the first number) of 140 or more, and/or diastolic blood pressure (the second number) of 90 or more.

-- Prehypertension: Systolic blood pressure of 120-139 and/or diastolic blood pressure of 80-89. People with this condition are at risk of developing high blood pressure and should take steps -- lose weight, exercise, and eat a healthy diet -- to help prevent that.

-- Normal adult (aged 18 or older): Systolic blood pressure of 119 or below and diastolic blood pressure of 79 or below.

High Blood Pressure More Common With Age

Data came from nearly 5,300 participants in the Framingham Heart Study, done in the 1990s. Three age groups were used: younger than 60, 60-79, and 80 or older.

High blood pressure became more common with age. Here are the high blood pressure percentages for each age group:

-- Younger than 60: 27 percent

-- 60-79: 63 percent

-- 80 and older: 74 percent

The percentages with normal blood pressure were:

-- Younger than 60: 39 percent

-- 60-79: 14 percent

-- 80 and older: 7 percent

Everyone else had prehypertension. Even people with prehypertension are at increased risk of developing heart problems.

Read WebMD's "Strategies to Prevent and Control High Blood Pressure"

Blood Pressure Risky for Blacks

The study's participants were mainly white. In the U.S., blacks tend to develop high blood pressure at an earlier age and have more severe cases than whites.

Blood Pressure Control Worst in Elderly Women

Few people (32 percent overall) had gotten their high blood pressure under control. "Control" meant getting blood pressure out of the "high" category, not all the way down to "normal."

Elderly women aged 80 and older were the least likely to have their high blood pressure under control. Fewer than one in four of them had gotten their high blood pressure under control.

Among men of the same age, 38 percent had their high blood pressure under control, the researchers write.

Lack of blood pressure control raises the chance of heart failure, heart attack, and stroke.

Read WebMD's "5 Steps to a Healthier Heart"

Drugs Used

Overall, nearly seven in 10 people with high blood pressure were getting treated. Most (60 percent) took one blood pressure drug, 30 percent used two, and 10 percent used three or more.

Water pills (diuretics) were underused as a blood pressure treatment, particularly among men, with newer blood pressure drugs getting "preferential prescription," write the researchers.

While the researchers don't question the safety and usefulness of those newer drugs, they note some advantages with diuretics.

There is "wealth of evidence suggesting that thiazide diuretics are the most cost-effective agents for blood pressure reduction, and that they are particularly efficacious among the elderly," write the researchers.

By Miranda Hitti, reviewed by Michael W. Smith, MD

SOURCES: Lloyd-Jones, D. The Journal of the American Medical Association, July 27, 2005; vol 294: pp 466-472. American Heart Association: "High Blood Pressure." WebMD Medical Reference from Healthwise: "High Blood Pressure (Hypertension)." WebMD Medical News: Water Pill Works Best for High Blood Pressure." News release, JAMA/Archives.