Impact of Diastolic and Systolic Blood Pressure on Mortality: Implications for the Definition of “Normal”
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The National Heart, Lung and Blood Institute currently defines a blood pressure under 120/80 as “normal.”
To examine the independent effects of diastolic (DBP) and systolic blood pressure (SBP) on mortality and to estimate the number of Americans affected by accounting for these effects in the definition of “normal.”
DESIGN, PARTICIPANTS AND MEASURES
Data on adults (age 25–75) collected in the early 1970s in the first National Health and Nutrition Examination Survey were linked to vital status data through 1992 (N = 13,792) to model the relationship between blood pressure and mortality rate adjusting for age, sex, race, smoking status, BMI, cholesterol, education and income. To estimate the number of Americans in each blood pressure category, nationally representative data collected in the early 1960s (as a proxy for the underlying distribution of untreated blood pressure) were combined with 2008 population estimates from the US Census.
The mortality rate for individuals over age 50 began to increase in a stepwise fashion with increasing DBP levels of over 90. However, adjusting for SBP made the relationship disappear. For individuals over 50, the mortality rate began to significantly increase at a SBP ≥140 independent of DBP. In individuals ≤50 years of age, the situation was reversed; DBP was the more important predictor of mortality. Using these data to redefine a normal blood pressure as one that does not confer an increased mortality risk would reduce the number of American adults currently labeled as abnormal by about 100 million.
DBP provides relatively little independent mortality risk information in adults over 50, but is an important predictor of mortality in younger adults. Conversely, SBP is more important in older adults than in younger adults. Accounting for these relationships in the definition of normal would avoid unnecessarily labeling millions of Americans as abnormal.
KEY WORDSblood pressure hypertension guidelines mortality
This material received no direct funding, but is the result of work supported with resources and the use of facilities at the Minneapolis and White River Junction VA Medical Centers. The views expressed herein do not necessarily represent the views of the Department of Veterans Affairs or the United States Government.
Conflicts of Interest
- 2.Effects of treatment on morbidity in hypertension. II. Results in patients with diastolic blood pressure averaging 90 through 114 mmHg. JAMA 1970; 213(7):1143–1152.Google Scholar
- 4.Prevention of stroke by antihypertensive drug treatment in older persons with isolated systolic hypertension. Final results of the Systolic Hypertension in the Elderly Program (SHEP). SHEP Cooperative Research Group. JAMA 1991; 265(24):3255–3264.Google Scholar
- 5.Chobanian AV, Bakris GL, Black HR, Cushman WC, Green LA, Izzo JL Jr, Jones DW, Materson BJ, Oparil S, Wright JT Jr, Roccella EJ. The seventh report of the Joint National Committee on prevention, detection, evaluation, and treatment of high blood pressure: the JNC 7 report. JAMA. 2003;289(19):2560–72.PubMedCrossRefGoogle Scholar
- 11.National Heart, Lung, and Blood Institute (NHLBI) National Institutes of Health. The Eighth Report of the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure (JNC 8). Available at: http://www.nhlbi.nih.gov/guidelines/hypertension/jnc8/index.htm. Accessed January 14, 2011.
- 12.CDC National Center for Health Statistics' website. Public Use Data Tape Documentation: Medical Examination: National Health and Nutrition Examination Survey, 1971–75. Available at: http://www.cdc.gov/nchs/data/nhanes/nhanesi/4233.pdf. Accessed January 14, 2011.
- 13.U.S.Census Bureau. Annual Estimates of the Resident Population by Sex and Five-Year Age Groups for the United States: April 1, 2000 to July 1, 2008. Available at: http://www.census.gov/popest/national/asrh/NC-EST2008-sa.html. Accessed January 14, 2011.