||Systolic Number Is Important
Clinical Advisory Statement From The Coordinating Committee Of The National High Blood Pressure Education Program
Clinical Advisory Statement
May is National High Blood Pressure Education Month. It also is the start of a major campaign to increase awareness of the dangers of high systolic blood pressure, also known as systolic hypertension. The campaign is being undertaken by the National Heart, Lung, and Blood Institute (NHLBI) and the National High Blood Pressure Education Program (NHBPEP), which it coordinates. The NHLBI is part of the National Institutes of Health.
The cornerstone of the campaign is the release by the NHLBI and the NHBPEP of a clinical advisory recommending that systolic blood pressure be emphasized in the diagnosis and treatment of hypertension in middle-aged and older adults. The clinical advisory appears in this month's issue of Hypertension: Journal of the American Heart Association.
The campaign also includes the launch this month of a new high blood pressure Web site, with separate gateways for the public, health professionals, and community organizations. The Web site can be reached through the NHLBI home page at www.nhlbi.nih.gov
"Systolic hypertension is a major health threat, especially for older Americans," said NHLBI Director Dr. Claude Lenfant. "While it cannot be cured, systolic hypertension can be treated and its complications prevented.
"Americans may have heard that diastolic blood pressure counts more," Lenfant continued. "That may be true for younger people. But we now know that, as people get older, systolic blood pressure becomes more important. May is National High Blood Pressure Education Month, and that's the perfect time to begin to sound the alarm–don't ignore your systolic. If you're middle aged or older, it's a better blood pressure indicator than diastolic of your risk of heart disease and stroke."
This clinical advisory statement from the Coordinating Committee of the National High Blood Pressure Education Program is intended to advance and clarify the recommendations of the Sixth Report of the Joint National Committee on the Prevention, Detection, Evaluation, and Treatment of High Blood Pressure (JNC VI).1 It addresses several interrelated issues that are of particular importance as people approach the later decades of life.
It is time to turn our attention to systolic BP as the principal BP component for diagnosis, risk stratification and therapeutic decision-making in middle-aged and older Americans. There is a strong relationship of age with systolic blood pressure (BP) and hypertensive target organ damage, yet fewer than one in four Americans have BP values at or below the JNC VI recommendations of 140/90 mmHg. New studies have found that the accuracy of diagnosis and staging of hypertension in older people is more precise using systolic BP alone rather than in combination with diastolic BP. Furthermore, risk stratification for major complications of hypertension (stroke, myocardial infarction, heart failure, and kidney failure) is much more accurate when systolic rather than diastolic BP is used. Unequivocal clinical trial data indicate that lowering systolic BP markedly improves morbidity and mortality in older people. Thus, achievement of optimal public health benefits requires a nationwide call-to-action to improve our current low rates of systolic BP control.
Age and BP in Industrialized Societies
Systolic BP increases steeply with age in industrialized Western societies, whereas diastolic BP increases until about age 55 and then declines2. Pulse pressure (systolic-diastolic BP difference) also widens with age.3 Both isolated systolic hypertension and wide pulse pressures in older people are manifestations of increased arterial stiffening, decreased vascular compliance, and diffuse arteriosclerosis.4 Both systolic and pulse pressures are therefore markers of age-related vascular target organ damage, both act as independent cardiovascular risk factors,5,6 and both therefore reflect similar diagnostic and prognostic information. After middle age, systolic hypertension (above 140 mmHg) is substantially more common than diastolic hypertension (above 90 mmHg).3 Increasing arterial stiffness inevitably accompanies aging in Western societies but the actual rate at which this change occurs can vary widely among different individuals.
Classification by Systolic BP Improves Diagnosis, Staging, and Risk Stratification
Systolic BP contributes more than diastolic BP to the accuracy of diagnosis and staging of hypertension in older Americans. Using the current JNC VI definition of hypertension (BP greater than 140/90 mmHg), analysis of the Framingham cohort revealed that systolic BP alone correctly classified BP stage in 91 percent of individuals who were potential candidates for antihypertensive therapy compared to 22 percent who were correctly classified using diastolic BP values.7
It has been known since the early reports from the Framingham Heart Study that systolic BP is more robust than diastolic BP as an independent cardiovascular risk factor.8 The preeminent value of systolic BP in risk prediction also was clearly demonstrated in the 316,000 men screened for the Multiple Risk Factor Intervention Trial (MRFIT),9 where the risk of coronary heart disease was linearly related to systolic BP elevation. In those with systolic hypertension, there was no clear relationship between diastolic BP and coronary risk. In those with normal systolic BP, increased coronary risk was found only in those whose diastolic BP exceeded 100 mmHg. Recent data from Framingham have underscored the prognostic significance of both systolic BP and pulse pressure as independent risk factors in older persons.6 In older individuals with systolic BP of 140 mmHg or greater, diastolic BP increases were inversely related to cardiovascular risk at any level of systolic BP.6 Thus, reliance on diastolic BP can confound diagnosis, staging, and risk assessment of hypertension using JNC VI guidelines.
Systolic BP is only slightly less powerful than pulse pressure as a risk predictor. Use of systolic BP for therapeutic follow-up is considerably more straightforward than pulse pressure, which has not yet been tested as a surrogate endpoint for morbidity or mortality in a prospective randomized clinical trial. Accordingly, this statement focuses on systolic BP rather than pulse pressure.
Clinical Trial Benefits of Systolic BP Control
Compelling data from two large placebo-controlled, double-blind, randomized clinical trials directly demonstrate the benefits of treating systolic hypertension (Table 1). The SHEP (Systolic Hypertension in the Elderly Program) trial investigated the value of thiazide diuretic-based treatment in individuals over 60 years of age whose initial BP values were above 160 mmHg systolic and below 90 mmHg diastolic.10 After five years of therapy, active treatment with diuretic (and beta-blocker if needed) reduced average systolic BP values about 14 mmHg more than placebo, with an overall systolic BP reduction from 171 to 142 mmHg. Compared to placebo, those randomized to diuretic treatment experienced marked reductions in the rates of myocardial infarction (-27 percent), heart failure (-55 percent), and stroke (-37 percent), as well as trends toward improvement in depression and dementia scores. In judging the relative benefit of systolic BP reduction in SHEP, it is noteworthy that the diastolic BP values in both study arms before and during therapy were about 76 and 70 mmHg, respectively. In a large European trial (Syst-EUR) in systolic hypertension, dihydropyridine calcium antagonist-based therapy caused reductions in systolic BP, stroke, and coronary events similar to those seen in SHEP.11
Current Trends in Treatment and Control
Of the 50 million Americans with hypertension in the U.S., only about half are currently treated with antihypertensive drugs and only about a quarter have both systolic and diastolic BP values at or below the target of 140/90 mmHg.2 Achievement of BP goals is even poorer in older Americans. In hypertensives over 70 years of age, 25 percent of African-Americans and 18 percent of white Americans have achieved the BP goals recommended by JNC VI.12 These data reveal that clinicians are willing to treat hypertension but are still not achieving desired goals, especially for systolic BP. Systolic BP almost always less well controlled than diastolic BP.13 Even in clinical trials, where aggressive management is required, systolic control rates are less than diastolic. In studies such as MRFIT and the Hypertension Optimal Treatment (HOT) trial, diastolic control rates exceeded 90 percent whereas systolic control rates were less than 60 percent.9,14
A critical public-health goal for the next decade remains the reduction of cardiovascular morbidity and mortality through aggressive multiple risk factor management. As the U.S. population ages, the burden of uncontrolled systolic hypertension will take an increasing toll on the health and well being of our society. Inadequate reduction of systolic BP and dismal systolic BP control rates are causally related to the continuing increase in heart failure deaths and hospitalizations among those over 65 years of age. Epidemiologic evidence has implicated systolic hypertension as a key risk factor for heart failure15 and clinical trials have demonstrated unequivocally that systolic BP control can prevent the development of heart failure.16 Systolic hypertension interacts with other major risk factors such as hypercholesterolemia and diabetes, which also increase in prevalence with age, to amplify the age-related risk of a cardiovascular event.17 Virtually all high-risk populations, including diabetics, benefit markedly from vigorous BP control.18 In high-risk groups, the number needed to treat (NNT) to demonstrate benefit (reflective of the absolute benefit of treatment), is substantially fewer than that found in low-risk groups.
The optimal BP target remains somewhat unclear at this time. Epidemiological data demonstrate a gradual increase in risk proportional to systolic BP with no major inflection point. SHEP demonstrated that treatment of systolic hypertension to systolic BP values below 160 mmHg improves outcomes16 but no trial to date has directly confirmed the degree of additional benefit that would be expected from lowering systolic BP to values of 140 mmHg or less. Indirect modeled data from the HOT study suggest that optimal benefit occurs at a BP of 138/82 mmHg in those with combined systolic and diastolic hypertension.14
Recommended BP Targets and Therapies
Based on existing epidemiological and clinical trial evidence, JNC VI BP targets remain in effect. In uncomplicated hypertension, BP should be treated to values below 140 mmHg systolic AND 90 mmHg diastolic. In hypertensives with diabetes or target organ damage (heart failure, coronary artery disease, or renal failure), BP should be brought below 130 mmHg systolic AND 85 mmHg diastolic. It must be emphasized that control of BOTH systolic and diastolic pressures is necessary to achieve optimal benefits of therapy. The clinical folklore that an appropriate systolic BP is "100 + Age" must be abandoned immediately.
Therapeutic recommendations from JNC VI are reaffirmed. In isolated systolic hypertension, as in any form of hypertension, the primary goal is to lower the BP using any approved agent that is effective, well tolerated, and appropriate for the clinical conditions present in that individual. Clinician judgment is paramount in the decision-making process. In the absence of overriding comorbidities, the clinician is encouraged to follow JNC VI recommendations. There is compelling clinical trial evidence that thiazide diuretics and long-acting calcium antagonists lower morbidity and mortality in isolated systolic hypertension. Lifestyle changes are also useful in helping older patients achieve BP goals.
It is acknowledged that certain elderly individuals, including those with severe longstanding systolic hypertension and exaggerated BP variability, present significant challenges to achievement of the recommended BP targets. Nevertheless, clinicians are encouraged to pursue the BP goal of <140/90 mmHg in order to avoid the problem not achieving optimum benefit in those patients for whom the 140/90 mmHg target is relatively easily reached. In truly resistant patients, clinicians are advised to proceed more slowly and to allow longer periods of time to reach goal but to persist in attempts to lower BP. Although it is reasonable to assume that partial BP control is preferable to none at all, it seems equally clear that lower is better in the vast majority of patients.
Table 1. Major Trials in Isolated Systolic Hypertension
(Treated vs Control)
SHEP= Systolic Hypertension in the Elderly Program10,16
Syst-EUR = European Trial in Systolic Hypertension14
CAD = coronary artery disease
CHF = congestive heart failure
CVD = cardiovascular disease
- Joint National Committee on Prevention Detection, Evaluation, and Treatment of High Blood Pressure. The Sixth Report of the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure (JNC VI). Arch Intern Med. 1997; 157:2413-2446.
- Burt VL, Whelton P, Roccella EJ, Brown C, Cutler JA, Higgins M, et al. Prevalence of hypertension in the US adult population: Results from the third national health and nutrition examination survey, 1988-1991. Hypertension 1995; 25:305-313.
- Sagie A, Larson MG, Levy D. The natural history of borderline isolated systolic hypertension. N Engl J Med. 1993; 329:1912-1917.
- O'Rourke M. Arterial stiffness, systolic blood pressure, and logical treatment of arterial hypertension. Hypertension 1990; 15:339-347.
- Madhaven S, Ooi WL, Cohen H, Alderman MH. Relation of pulse pressure and blood pressure reduction to the incidence of myocardial infarction. Hypertension 1994; 23:395-401.
- Franklin SS, Khan SA, Wong ND, LarsonM.G., Levy D. Is pulse pressure more important than systolic blood pressure in predicting coronary heart disease events. Circulation 1999; 100:354-360.
- Lloyd-Jones DM. Impact of systolic versus diastolic blood pressure level of JNC-VI blood pressure stage classification. Hypertension 1999; 34:381-385.
- Kannel WB, Gordon T, Schwartz MJ. Systolic versus diastolic blood pressure and risk of coronary heart disease. American Journal of Cardiology 1971; 27:335-345.
- Neaton JD, Wentworth D for the MRFIT Research Group. Serum cholesterol, blood pressure, cigareet smoking, and death from coronary heart disease: Overall findings and differences by age for 316,099 white men. Arch Intern Med. 1992; 152:56-64.
- SHEP Cooperative Research Group. Influence of long-term, low-dose, diuretic-based, antihypertensive therapy on glucose, lipid, uric acid, and potassium levels in older men and women with isolated systolic hypertension: The Systolic Hypertension in the Elderly Program. Arch Intern Med. 1998; 158:741-751.
- Staessen JA, Thijs L, Fagard R, O'Brien EG, Clement D, de Leeuw PW, et al. Predicting cardiovascular risk using conventional vs ambulatory blood pressure in older patients with systolic hypertension. Systolic Hypertension in Europe Trial Investigators. JAMA 1999; 282:539-546.
- Burt VL, Cutler JA, Higgins M, Horan MJ, Labarthe D, Whelton P, et al. Trends in the prevalence, awareness, treatment, and control of hypertension in the adult US population. Data from the health examination surveys, 1960 to 1991. Hypertension 1995; 26:60-69.
- Berlowitz DR, Ash AS, Hickey EC, Friedman RH, Glickman M, Kader B, et al. Inadequate management of blood pressure in a hypertensive population. N Engl J Med. 1998; 339:1957-1963.
- Hansson L, Zanchetti A, Carruthers SG, et al.for the HOT Study Group. Effects of intensive blood-pressure lowering and low-dose aspirin in patients with hypertension: principal results of the Hypertension Optimal Treatment (HOT) randomized trial. Lancet 1998; 351:1755-1762.
- Levy D, Larson MG, Vasan RS, Kannel WB, Ho KKL.
The progression from hypertension to congestive heart failure: Insights into the time, course of and risk factors for hypertensive left ventricular dysfunction. JAMA 1996; 275:1557-1562.
- Kostis JB, Davis BR, Cutler J, Grimm RH, Jr., Berge KG, Cohen JD, et al. Prevention of heart failure by antihypertensive drug treatment in older persons with isolated systolic hypertension. SHEP Cooperative Research Group. Lancet 1997; 351:1755-1762.
- Wilson PWF, D'Agostino RB, Levy D, Belanger AM, Silbershatz H, Kannel WB. Prediction of coronary heart disease using risk factor categories. Circulation 1998; 97:1837-1847.
- UK Prospective Diabetes Study Group. Tight blood pressure control and risk of macrovascular and microvascular complications in type 2 diabetes (UKPDS 38). Br Med J. 1998; 317:713-720.