Although hypertension is known to be a risk factor for cardiovascular death, it appears that systolic blood pressure - the top number of the BP reading - is generally the most predictive of cardiovascular risk, researchers at the VA Health Care System in Boston report.

“We found that an elevated systolic blood pressure was the most important blood pressure parameter for predicting cardiovascular death across a wide age range,” said lead investigator, Dr. Thomas S. Bowman.

The systolic BP indicates how hard the heart is working during a beat while the diastolic - the bottom number - indicates pressure in major arteries when the heart rests between beats.

Bowman and colleagues conducted a prospective study of more than 53,000 participants in the Physicians’ Health Study cohort.

Over a median follow-up of 5.7 years, there were 459 cardiovascular deaths. For each 10 millimeters of mercury increase in systolic blood pressure, the risk ratio rose from 1.46 in the youngest group (39 to 49 years) to 1.13 in the oldest group (70 to 84 years).

For diastolic BP, the corresponding ratios were 1.25 and 1.07, the researchers report in the American Journal of Hypertension.

“Our findings emphasize the clinical importance of using systolic blood pressure to determine who is at risk for dying from cardiovascular disease,” Bowman concluded.

SOURCE: American Journal of Hypertension, January 2006.