Last month I criticized Gina Kolata, who wrote
a New York Times article that trumpeted the results of a large blood pressure treatment study, for weighing in on a study before it was actually published.
The Systolic Blood Pressure Intervention Trial (SPRINT) trial was stopped prematurely because subjects in the intensive treatment group (the aim was to study the benefits of a lower blood pressure target) had a significantly lower incidence of cardiovascular complications than the usual treatment group (target systolic pressure: 120 mmHg, as opposed to the current 140 mmHg).
In what must be a new world speed record, the New England Journal of Medicine reviewed and published
the study on Nov. 9.
I was right to be cynical about this study; it is fraught with problems.
First, it was open-label, or unblinded. This means that patients and physicians knew what treatment group they were in. Blinding is an important element of study design because it reduces investigator bias. As John Iaonnidis teaches us (see last month’s post
) bias can determine the study outcome, particularly when the treatment effect is small, as it is here.
Second, SPRINT used a composite endpoint, which is a laundry list of cardiovascular outcomes, as opposed to a single endpoint.
This is done to magnify the effect of an intervention where the actual incidence of individual outcomes is low. In other words, it’s a gimmick to get a “statistically significant” result.
Third, a monitoring committee stopped the study years ahead of schedule, presumably because the intensive treatment arm achieved a statistically significant reduction in the composite outcome. But this downplays the side effects, which tend to increase over time.
Fourth, patients with diabetes were excluded. This group makes up a large segment of the hypertension population, and has been studied in the Action to Control Cardiovascular Risk in Diabetes (ACCORD
) trial. Interestingly, in this study, there was no benefit to intensive blood pressure treatment (and intensive blood sugar control was associated with higher mortality).
Fifth, and perhaps most important, the intensive treatment group achieved the composite endpoint at a rate of 1.65 percent per year, as opposed to 2.19 percent in the standard treatment arm. Thus, while the Times reported that the intensively treated patients “had their risk of heart attacks, heart failure, and strokes reduced by a third,” the actual risk reduction was 0.54 percent. With the large number of patients enrolled (more than 9,000), this achieved statistical significance.
Sixth, serious side effects such as kidney failure, low blood pressure, electrolyte disturbances, and fainting, were more common in the intensively treated patients.
When the actual risk reduction is so small, the “number needed to treat” to prevent one bad outcome necessarily becomes large. The authors report that to prevent one death from cardiovascular causes, 172 patients would need to be treated over three years. And 171 of these would be subjected to myriad side effects without benefit.
Not a great model for health.
The SPRINT study is a classic example of so-called “evidence-based medicine.” This flawed trial will no doubt be used to promote more aggressive treatment of hypertension in general, and will almost certainly lead to many more complications, and diminished quality of life, with little or no benefit.
I would like to see a study comparing standard treatment of mild to moderate hypertension using medications with the Mediterranean diet, coupled with exercise.
From my own practice, I can tell you how such a study would turn out. The majority of hypertensive (and diabetic) patients can be successfully treated with healthy diet and exercise. Drug therapy only rarely addresses the underlying disease state and should not be overused.
Physicians should continuously stress lifestyle and diet modification to their patients, and strive to reduce their medication burden.
Dr. Amerling is board certified by the American Board of Internal Medicine for Internal Medicine and Nephrology. He also is president of the Association of American Physicians and Surgeons. For more of his reports, Go Here Now.
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