Rising systolic blood pressure is the clearest indicator for increased risk of death compared to other blood pressure measurements, according to researchers at the Johns Hopkins Bloomberg School of Public Health. Their evaluation of blood pressure measurements and mortality risk found that diastolic and pulse pressure measurements were weaker indicators of mortality risk and their effect was more dependent on age and other factors. The study appears in the November 4, 2003, edition of the Annals of Internal Medicine.
Systolic pressure, which is the higher number and first number in a blood pressure reading, measures the force of blood in the arteries as the heart contracts to push blood through the body. Doctors consider a systolic blood pressure greater than 120 mm Hg (millimeters of mercury) as unhealthy and can lead to heart disease, stroke and vascular diseases of the legs. Diastolic pressure, the lower number, measures the pressure as the heart relaxes to fill with blood. A diastolic pressure greater than 80 mm Hg is also considered unhealthy. Pulse pressure is the difference between the diastolic and systolic readings.
"There is some controversy in the medical community over whether the monitoring of systolic, diastolic, or pulse pressure should be the focus in treating hypertension. Our study shows that an increased systolic reading is most closely associated with an increased risk of death," said lead investigator Eliseo Guallar, MD, DrPH, an assistant professor in the School's Department of Epidemiology.
The study included 7,830 white and African American adults age 30 to 74 that took part in the Second National Health and Nutrition Examination Survey (NHANES II) from 1976 to 1992. All of the participants were free of an obvious heart disease. Blood pressure was measured three times at enrollment. Of the 1,588 participants who died, 582 died of cardiovascular disease.
Dr. Guallar and his colleagues studied the effects of high systolic and diastolic blood pressure simultaneously and found a direct and consistent correlation between increased systolic blood pressure and an increased risk of death from cardiovascular disease and for all other causes among all of the study participants. Increased diastolic pressure over 80 mm Hg was also associated with an increased risk of death. However, for people under 65, the risk of death remained the same for diastolic reading of 80 mm Hg or lower. For participants over 65 years of age, the risk of death increased with low diastolic pressure.
The researchers found a complex association between pulse pressure and mortality. Increasing pulse pressure caused by increased systolic pressure was associated with an increased risk of mortality. Decreased pulse pressure caused by increased diastolic pressure could be associated with increased risk, decreased risk, and no change in the risk of mortality.
"Pulse pressure alone, without appropriate attention to systolic and diastolic blood pressure components, is an inadequate indicator of mortality risk," said Dr. Guallar.
"Systolic Blood Pressure, Diastolic Blood Pressure, and Pulse Pressure: An Evaluation of Their Joint Effect on Mortality" was written by Roberto Pastor-Barriuso, PhD; José R. Banegas, MD, PhD; Javier Damián, MD, PhD; Lawrence J. Appel, MD, MPH; and Eliseo Guallar, MD, MPH.
Funding was provided by the Instituto de Salud Carlos III, Madrid, Spain. Study investigators work at the National Center for Epidemiology, Instituto de Salud Carlos III, Madrid, Spain; Universidad Autónoma de Madrid, Spain; and Johns Hopkins Medical Institutions.
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