It's taken as gospel among doctors: Treat high blood pressure aggressively to avoid heart attacks, strokes, and other cardiovascular problems.
The magic numbers have been 120/80 — or 120 over 80 — representing both the level of pressure during and between heart beats.
But in the drive to lower the top (systolic) number, doctors may be inadvertently lowering the bottom (diastolic) number too much.
A 21-year study of the medical records of thousands of patients by Johns Hopkins Medicine has found a link to heart damage.
The researchers say they can't prove low diastolic pressure directly causes the damage, only that they see more of it as that measure drops.
"The take-home message is there is increased likelihood that if we use blood pressure drugs to push patients' systolic blood pressures down to 120, which is a strategy supported by recent clinical trials, the consequence in those starting out with low diastolic blood pressures (e.g., below 80) may be that the diastolic number falls so low that we risk doing damage," J. William McEvoy, assistant professor of medicine and member of the Ciccarone Center for the Prevention of Heart Disease at the Johns Hopkins University School of Medicine, said in a statement.
The findings, published in the Journal of the American College of Cardiology, suggest that doctors may need modify their intensive treatment to reduce the top number and consider affects to the bottom number. For some people, the low pressure may not be sufficiently pumping blood to nourish the heart muscle.
About 70 million Americans, or one in three, has high blood pressure, according to the U.S. Centers for Disease Control and Prevention. Heart disease is the nation's No. 1 killer.