Current guidelines for the prevention and treatment of high blood pressure acknowledge the critically important relationship between systolic blood pressure, diastolic blood pressure and cardiovascular risk. 'This relationship is strong, continuous, graded (and)... predictive...for those with and without coronary heart disease,' notes the Sixth Report of the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure (JNC VI). A study funded by the National Heart, Lung, and Blood Institute (NHLBI) and published in the January 15 issue of the Lancet challenges JNC VI by asserting that the relationship between systolic blood pressure and mortality is not "continuous and graded." After careful review of this study, the NHLBI finds that it does not offer a basis for changing the current hypertension guidelines.
Dr. Sidney Port and co-authors of the study base their conclusions on a re-analysis of data from NHLBI's long-running Framingham Heart Study. Dr. Port concludes that risk of death was unrelated to systolic pressure up to approximately the 70th percentile of systolic blood pressure for each person of a given age and gender. Risk then rapidly increases for those with pressure above the 80th percentile pressure, according to Dr. Port. Based on this finding, Dr. Port suggests a reclassification of hypertension cut points, which would be based on these percentiles and factor in a person's age and sex. He concludes that the linear model on which current treatment guidelines are based results in an overestimate of the risks in the midrange of pressures - approximately 130 to 170 mm Hg. Dr. Port suggests that people who are treated at the current threshold for treatment, which is 140 mm Hg, may be taking antihypertensive medication unnecessarily. Dr. Port also notes that clinical trials of isolated systolic hypertension did not include people with systolic blood pressure below 160 mm Hg and that therefore, giving antihypertensive drugs 'to persons solely on the basis that their systolic blood pressure exceeds 140 mm Hg is not justified.'
We attach great value to new scientific findings and our careful review of Dr. Port's paper finds his analysis thought provoking. However, we would not recommend a change in the guidelines based on one epidemiological analysis. JNC VI was prepared by a multidisciplinary expert panel that reviewed all of the available evidence from not only clinical trials - often referred to as the gold standard of scientific research - but also from observational studies, basic research, and epidemiological studies - including all of the Framingham data. The totality of evidence found a clear linear relationship between systolic blood pressure, diastolic blood pressure and deaths. Based on this review, JNC VI defined hypertension as systolic blood pressure averages of 140 mm Hg or greater and/or diastolic blood pressure averages of 90 mm Hg or greater. JNC VI also examined the frequeny of serious nonfatal events such as stroke and heart attack and the panel found the same linear relationship for these events.
Treatment recommendations are not based solely on a patient's blood pressure level. The guidelines state that the presence of other risk factors for coronary heart disease and the presence of atherosclerosis must be considered when deciding whom and how to treat. Patients with several risk factors who are at higher risk for a heart attack or stroke should be prescribed drugs at lower blood pressure levels than patients who have no other risk factors. This approach recognizes that multiple factors are responsible for the development and acceleration of cardiovascular disease. Thus, an older male patient who has a systolic blood pressure of 140 mm Hg, diabetes, and heart failure, is clearly managed in a different way from someone with a similar blood pressure level but no other risk factors. JNC VI acknowledges that each patient must be carefully evaluated and physicians must use their best judgment to make individualized treatment decisions.
Hypertension, which affects about 50 million Americans, continues to be a major public health issue. Untreated hypertension can damage the kidneys and lead to stroke, heart attack, and heart failure. Treating hypertension can reduce the risk for these conditions.
Despite momentous declines in mortality from heart disease and stroke over the past 30 years, these diseases are still the first and third leading causes of death, respectively, in the U.S. The NHLBI is strongly committed to combating these leading killers. Thus, the Institute will continue to support and critically evaluate new research on hypertension. Scientific research is the foundation on which NHLBI makes recommendations to clinicians.