NEW YORK, Mar 15 (Reuters Health) - For a majority of people with high blood pressure (BP), the systolic or upper number in the blood pressure reading is a more important measure of their risk of heart attack and stroke. However, many people with systolic elevations do not have their blood pressure adequately controlled, researchers report.

As people age, their systolic blood pressure naturally increases, while their diastolic pressure begins to dip around age 55. A systolic pressure below 120 millimeters of mercury (Hg) and a diastolic below 80 are considered a healthy overall blood pressure. Among older adults, the most common form of high blood pressure is isolated systolic hypertension, in which only the upper number is elevated above normal.

In the past, doctors believed that the more important reading was the diastolic pressure (the lower number in the conventional blood pressure reading), which reflects blood pressure of the heart at rest (between contractions). Systolic pressure indicates the force generated during the heart's contraction.

Over the past few decades, however, investigators determined that systolic pressure is key in gauging patients' risk of heart disease, stroke and kidney failure. Achieving control of systolic blood pressure in older individuals has become an important treatment goal.

But new research on high blood pressure among middle-aged and older Americans suggests that isolated systolic hypertension is often uncontrolled. And one reason may be that many doctors are hanging on to the traditional idea that controlling diastolic pressure is sufficient, according to Dr. Nathan D. Wong, one of the authors of a report published in the March issue of Hypertension: Journal of the American Heart Association.

"Doctors over the years have been biased to controlling diastolic blood pressure, and (some) may remain satisfied with that even if the systolic isn't controlled," Wong said in an interview with Reuters Health.

Wong, a researcher at the University of California, Irvine, and his colleagues examined a national database of health information on nearly 20,000 Americans who were surveyed between 1988 and 1994. The research team found that among adults with high blood pressure, 80% of those aged 50 and older had isolated systolic hypertension.

More than three fourths of those with high blood pressure were either untreated or inadequately treated, and in 65% of these cases, patients had isolated systolic hypertension.

Adequate treatment, Wong explained, means getting patients' elevated pressure to the "minimum goal" of below 140/90 mm Hg.

And, according to Wong, there is a greater push to lower patients' blood pressure beyond the minimum treatment goal. "We should strive for the optimal level of less than 120/80," he said.

To do that, he added, doctors will have to do a better job of advocating lifestyle changes such as cutting fat from the diet, getting more exercise and quitting smoking. Some patients, Wong said, may need treatment with more than one blood pressure-lowering drug.

Two co-authors on the study are from the Princeton, New Jersey-based Bristol-Myers Squibb, which markets several blood pressure drugs.

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