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A new study is turning decades of medical dogma on its head. A panel of independent experts reports this week that drugs used to treat mild cases of high blood pressure have not been shown to reduce heart attacks, strokes, or overall deaths.
Most of the 68 million patients in the United States with high blood pressure have mild, or Stage 1, hypertension, defined as a systolic (top number) value of 140-159 or a diastolic (bottom number) value of 90-99. The new review suggests that many patients with hypertension are overtreated - they are subjected to the possible harms of drug treatment without any benefit.
The study was conducted by the widely respected Cochrane Collaboration, which provides independent analyses of medical data. The "independent" part is important: The panelists who conducted the analysis don't take money from drug companies.
Since many doctors and professional societies have been promoting treatment for mild hypertension for decades, the astute reader might wonder why this analysis was conducted only recently. The reasons are complex, but in a nutshell, researchers simply never addressed the question: Does treatment of mild hypertension help or harm patients? Instead, many authorities simply assumed that treatment helped, probably because treatment of more severe hypertension has been shown to be beneficial. In most clinical trials, patients with all degrees of hypertension were simply lumped together.
The Cochrane reviewers extracted data from all prior clinical trials to date that included test subjects treated for mild hypertension. They analyzed the outcomes of drug treatment (compared to no treatment or placebo) for nearly 9,000 patients with mild hypertension. James Wright, coordinating editor of the Cochrane Hypertension Group, told Slate that his group's analysis doesn't preclude the possibility that a larger study might find a small degree of benefit that was not apparent from the available data. But the fact that no benefit was detected in the Cochrane analysis means that any benefit is likely to be small - if present at all. And there's always the possibility that the drugs cause a slight net harm. Some of the drugs are known to cause serious complications, including death.
A problem known as "disease creep" may explain the Cochrane findings. Disease creep occurs when patients with risk factors for a condition or milder cases are treated the same as patients with severe cases. Most patients with mild disease would do well in any case, so it's easy for drug side effects to overwhelm any benefit.
Jay Siwek, editor of the journal American Family Physician, notes that disease creep can be seen in the recently created concept of "predisease" - such as "prehypertension" or "prediabetes." Starting medication in people who have only a risk factor, even before they have any evidence of actual disease, can greatly increase profits by getting more people on medicines for far longer periods of time.
Jerome Hoffman, emeritus professor of medicine at UCLA and an expert in critical appraisal of medical literature, points out that almost all benefit from treating severe hypertension comes with lowering blood pressure just a little. A determined effort to lower blood pressure further, all the way to "normal," typically requires multiple drugs and is not only usually unsuccessful but also very likely produces more harm than good, since adverse effects of intensive treatment outweigh the minimal, marginal benefit of a little more blood pressure reduction. "Drug treatment of mild hypertension, like intensive treatment of severe hypertension, may be of great value to drug makers," Hoffman says, "but it was almost predictable that it would provide little or no benefit for patients."
Not everyone agrees with the Cochrane review's conclusions. William White of the University of Connecticut School of Medicine and president of the American Society of Hypertension. says the analysis included too few studies and too few patients to draw any reliable conclusions. He also says the studies were too short to yield meaningful results for patients with hypertension.
White says that the number of strokes was lower in patients who were treated for mild hypertension than in those who were not, but he acknowledges that the difference was not statistically significant. That means the difference may well have been due to chance rather than any effect of treatment. But he says this is because of the low number of strokes overall, and therefore he claims it is incorrect to say that treatment doesn't prevent strokes. Wright, of the Cochrane group, counters that there was also a nonsignificant trend toward more heart attacks among treated patients. But this also might have been due to chance, and any claim about decreasing strokes would have to be accompanied by equal acknowledgment of increasing heart attacks - neither of which may be true. Wright cautioned, "If we made decisions based on 1/8data like that 3/8, we'd make more mistakes than we already make."
Hoffman, of UCLA, says that it is always possible to dismiss "inconveniently negative" evidence, like that in the Cochrane review, because no study can test every possible dosage or combination of medicines or duration of treatment. Thus it is always technically possible that some untested formula might work. But he calls the Cochrane review "the best evidence currently available" about the effects of drug treatment on patients with mild hypertension and says that its results fit with what is known about diminishing returns - and the potential for dangerous side effects - when treating people with less severe disease. He also objects to the idea of treating "unless and until we know for sure that it's a bad idea," suggesting instead that "we shouldn't subject patients to possible harm unless and until we have reasonably good evidence that it's worth doing."
Given the possibility that future trials will identify at best a small, currently nonapparent benefit, it seems clear that the best thing for doctors to do would be simply to tell patients the truth - that while the best current evidence doesn't support routine treatment of mild hypertension, we really don't know for sure. But we do know this: Emphasizing far more effective - and evidence-based - approaches, such as exercising, quitting smoking, and following a Mediterranean diet, seems to be a very good idea. And besides, they work.