For years doctors thought it was more important to try to lower the bottom, or diastolic, number to reduce the health risks of high blood pressure, including heart disease, stroke and kidney failure.
While many doctors still focus on diastolic readings, recent research has suggested that the top, or systolic, measure, is more important, especially in the elderly. The new study extends those findings to men aged 52 on average.
The results are published in Monday's archives of Internal Medicine.
The systolic reading represents pressure when the heart beats; the diastolic shows pressure in between beats when the heart relaxes. Optimal blood pressure is 120 over 80 or lower.
High blood pressure — 140 over 90 or higher — affects more than 50 million U.S. adults.
In the French study, men with systolic readings of 160 or higher faced more than double the risk of dying from cardiovascular disease during an average follow-up of 14 years, compared with men whose systolic numbers were under 140. Those with systolic numbers between 140 and 160 faced a lower but still increased risk.
There was no increased cardiovascular risk for men with elevated diastolic numbers.
"Diastolic blood pressure, which remains the main criterion used by most physicians in determining drug efficacy, appears to be of little value in determining cardiovascular disease risk," wrote the authors, led by Dr. Athanase Benetos at the Center for Preventive and Clinical Investigations in Paris.
An Archives editorial said the study is important "because the prevailing thinking is that systolic blood pressure is primarily important in the elderly." The study shows that it's also important in middle-age men, said the editorial author, Dr. Prakash Deedwania of the University of California, San Francisco.
Many recent studies have shown that patients whose diastolic pressure is controlled with drugs often still have elevated systolic pressure, Deedwania said. This may reflect some doctors' willingness to accept higher-than-recommended blood pressure measurements, and a reluctance by some to prescribe two or more blood pressure medications — which may be needed for adequate control, he said.
By Lindsey Tanner