"Our results indicate the importance of lowering blood pressure in everyone over a certain age, rather than measuring it in everyone and treating it in some," they declared in an online report in BMJ.
According to Malcolm Law, M.B.B.S., of the Wolfson Institute of Preventive Medicine at Barts and The London School of Medicine and Dentistry, a meta-analysis of 147 clinical trials over four decades disclosed that all major classes of antihypertensives reduce the risk of cardiovascular events and stroke equally, regardless of the patient's history of coronary heart disease and hypertension. The benefits of antihypertensives are almost entirely due to lowering blood pressure, they said.
The results lead to "the logically inescapable conclusion that there is then little or no gain in routinely measuring a person's blood pressure -- a conclusion that will undoubtedly stimulate discussion since it is at variance with 100 years of medical practice," they said.
Two prominent British researchers, Richard McManus, M.B.B.S., Ph.D., of the University of Birmingham, and Jonathan Mant, M.B.B.S., M.D., of the University of Cambridge, agreed with the investigators' conclusion.
"The place of the sphygmomanometer in the doctor's office for monitoring blood pressure lowering treatment no longer seems secure," they wrote in an accompanying editorial.
"It may perhaps be replaced by intermittent but infrequent blood pressure measurement at home, supplemented by periodic enquiry about side effects as treatment choices become determined by tolerability rather than algorithm," they said.
Timothy Gardner, M.D., a cardiothoracic surgeon and president of the American Heart Association, called the researchers' conclusions overly aggressive. "I think this idea that you just treat everybody is overkill," he said.
Lifestyle changes, such as increasing physical activity, losing weight, drinking less alcohol, and eating a healthier diet, are effective for many patients who are hypertensive or borderline, he said. If patients do need medication to lower blood pressure, treatment often must be personalized because different classes of drugs produce different side effects, he said.
The researchers sought to quantify the effect of the five major classes of blood pressure medications -- thiazides, beta-blockers, angiotensin converting enzyme inhibitors, angiotensin receptor blockers, and calcium channel blockers -- on lowering the risk of cardiovascular events and stroke.
Dr. Law and colleagues conducted a meta-analysis of 147 randomized controlled trials from 1966 through 2007. Overall, the studies included 464,000 patients. They said relative risks were calculated using an assumed 10-mm Hg reduction in systolic pressure and 5-mm Hg reduction in diastolic pressure.
The major findings included:
- Treatment with beta-blockers resulted in an added protective effect (over blood pressure lowering effects) against cardiovascular events in patients with a history of coronary heart disease during the first two years after MI (29% reduction in risk with beta-blockers versus 15% reduction with other antihypertensives, P<0.001). After two years, the benefit was similar to other classes.
- In trials of all other drug classes, there was a 22% reduction in coronary heart disease events (RR 0.78, 95% CI 0.73 to 0.83) and a 41% reduction in stroke (RR 0.59, 95% CI 0.52 to 0.67). These figures are similar to those found in a large meta-analysis of cohort studies, "indicating that the benefit is explained by blood pressure reduction itself," the researchers said.
- In general, all five drug classes had similar effectiveness for preventing coronary heart disease events and strokes, except for a small added benefit with calcium channel blockers for preventing stroke (P=0.01).
- The benefits were consistent across patient groups, regardless of the presence of cardiovascular disease and high blood pressure.
- All drug classes lowered the risk of heart failure, although calcium channel blockers reduced risk to a lesser extent than the others (19% versus 24%, P<0.001).
"Guidelines on the use of blood pressure lowering drugs can be simplified so that drugs are offered to people with all levels of blood pressure," the researchers said.
In a separate analysis combining the results of the meta-analysis with two previous meta-analyses, Dr. Law and colleagues determined that taking three antihypertensives together, each at half the standard dose, reduced the risk of coronary heart disease events by 46% and of stroke by 62%. One drug at the standard dose had about half the effect, they said.
Drs. McManus and Mant, however, cautioned that "no trials have tested combinations of three drugs at half standard dose, and their analysis assumes that the effects are additive."
But, the editorialists said, "Taken at face value, these findings provide tacit support for the use of a 'polypill' to lower the risk of cardiovascular disease in people likely to be at high risk (such as all people over the age of 55) without first checking their blood pressure."
Dr. Law and colleagues acknowledged that the meta-analysis was subject to limitations stemming from the lack of individual patient data from the included trials.
Explain to interested patients that the authors of this study said all individuals at risk for cardiovascular or cerebrovascular disease should be given routine treatment with blood pressure lowering drugs, regardless of blood pressure
BMJ 2009;338;b1665; doi:10.1136/bmj.b1665
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