Diastolic blood pressure measures the pressure in your blood vessels between heartbeats, when your heart is resting. It is represented by the bottom number in a blood pressure reading. Systolic blood pressure measures the amount of pressure that blood exerts on vessels while the heart is beating. It is represented by the top number in a blood pressure reading.
The study coined and defined the term “isolated diastolic hypotension,” which occurs when the diastolic blood pressure is low (less than 60 mm Hg) and the systolic blood pressure is not low (above 100 mm Hg). This is similar to a condition called isolated systolic hypertension, when the systolic blood pressure alone is elevated (above 140 mm Hg) but the diastolic blood pressure is not elevated (less than 90 mm Hg). This condition is common in older adults and also is a risk factor for heart failure.
“Our findings showed that older adults who have low diastolic blood pressure but not low systolic blood pressure were more likely to develop new-onset heart failure than those with higher levels of diastolic blood pressure,” said Ali Ahmed, M.D., professor of medicine in the Division of Gerontology, Geriatrics and Palliative Care, director of the UAB geriatric heart-failure clinic and the study’s senior investigator. “Older adults with low diastolic blood pressure also had higher risk of death.”
Ahmed and colleagues say that isolated diastolic hypotension can also occur in patients with high systolic pressure who are controlling their high blood pressure with medications.
“This may become a dilemma for physicians when treating these patients,” said Jason Guichard, M.D., Ph.D., a cardiology fellow and the lead author of the study. “It may be difficult to find the appropriate dosage of anti-hypertensive medications that will reduce the systolic blood pressure to normal levels to below 140 mm Hg, without reducing diastolic blood pressure to below 60 mm Hg.”
“Unfortunately, when the diastolic blood pressure is low in the absence of any anti-hypertensive medications, there is little that can be done,” said Ahmed, who is also a senior scientist at the UAB Center for Aging. “Whether addressing other risk factors for heart failure would reduce the risk of heart failure in these individuals remains unclear.”
Ahmed and Guichard say additional research is necessary to establish guidelines for optimal diastolic blood pressure parameters for older adults, particularly for those using anti-hypertensive medications.
The study was conducted with 545 older adults with isolated diastolic hypotension and 2,348 propensity-matched older adults without isolated diastolic hypotension who were balanced on 58 baseline characteristics that included many traditional risk factors for heart failure. They were enrolled in the Cardiovascular Health Study, a large population-based epidemiological study of Medicare-eligible older adults recruited from four communities within the United States during 1992-1993 and were followed for more than 12 years.
The study was funded by the National Heart, Lung and Blood Institute, one of the National Institutes of Health.
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