Dr. Brent Taylor of the Veterans Affairs Health Care System in Minneapolis and the University of Minnesota and colleagues examined the independent contribution of diastolic blood pressure and systolic blood pressure on mortality.
The research team said those with abnormal blood pressure are not more likely to die prematurely than those with normal blood pressure -- below 120/80 millimeters of mercury.
However, the findings also show for those under age 50, diastolic blood pressure (lower number) is the more important predictor of mortality, but for those age 50 and older, systolic blood pressure (upper number) is the stronger predictor, Taylor said.
Taylor and colleagues argue in the Journal of General Internal Medicine it is time to consider a new definition of normal blood pressure.
The researchers looked at data for 13,792 people from the National Health and Nutrition Examination Survey, which enrolled participants in 1971 to 1976 and followed them up for two decades. They also looked at data for 6,672 adults from the first National Health Examination Survey carried from 1959 to 1962.
"Our findings highlight that the choice of approach used to define normal blood pressure will impact literally millions of Americans," Taylor said in a statement.
"If we cannot reliably see an effect on mortality in a large group of individuals followed for nearly 20 years, should we define the condition as abnormal?"
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