The ENCORE trial, a 4-month lifestyle intervention published in 2010, showed reduction in BP similar to that achievable by drugs. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3633078/
Subjects were assigned to three groups: usual diet (UC), DASH alone (DASH-A), and DASH plus weight management (DASH-WM).
The reductions in blood pressure were 3.4/3.8 mm Hg (systolic/diastolic) for UC, 11.2/7.5 mm Hg for DASH-A, and 16.1/9.9 mm Hg for DASH-WM.
16.1/9.9 mm Hg reduction in blood pressure! That’s a lot.
For reference, the average BP reduction of drugs is 12.5/9.5 mm Hg.
By drug class, that’s:
Alpha1-blockers 15.5/11.7 mm Hg;
Beta1-blockers by 14.8/12.2 mm Hg;
Calcium channel blockers by 15.3/10.5 mm Hg;
Thiazide diuretics by 15.3/9.8 mm Hg; and
Loop diuretics by 15.8/8.2 mm Hg.
So this trial’s strongest intervention’s impact is approximately the same as that of commonly prescribed blood pressure medications. And because it is a lifestyle intervention instead of a drug, its benefits are likely to extend beyond that of blood pressure.
And the disease prevention potential is likely to be substantial. As authors write: “Similar BP reductions have been achieved in placebo-controlled treatment trials and have resulted in a lowering of stroke risk by approximately 40% and a reduction in ischemic heart disease events by about 25%.”
But so what? This trial was conducted in a manner quite alien from how most medical practices might try to implement such lifestyle changes:
- Subjects underwent 2 weeks of controlled feeding according to their assigned intervention;
- During this, they met with a nutritionist twice per week;
- They were weighed every other day during this period;
- They were given a precise estimate of calorie intake based on sophisticated research models;
- Following this first 2 weeks, they were weighed and met for 30 to 45 minutes in small group with a nutritionist every week for the next 14 weeks, making adjustments in intake to meet study targets;
- DASH-WM subjects received an additional weekly cognitive-behavioral weight loss intervention and attended supervised exercise sessions 3 times per week.
Here are the details on #6:
That is a lot of behavioral intervention.
Correspondingly, reported adherence was high. In the discussion, authors write:
“The BP reductions achieved in our DASH-A and DASH-WM interventions were greater than those described in the PREMIER study and in other trials of lifestyle modification. The reasons for the greater benefit from the current ENCORE intervention could be attributed to the greater weight loss and excellent adherence to the DASH diet and exercise sessions.”
In other words, the behavioral intervention counted for a substantial portion of the effect.
Just how useful, therefore, is this study? Sure, weight loss, physical activity, etc. reduce hypertension. But if a clinical trial’s intervention is so far outside of the scope or practicality of clinical practice, because it relies on such an intensive behavioral intervention, what use are the study’s findings?
What, for instance, is the long-term adherence to this diet in the real world?
Likewise, are there any ways to ensure such long-term adherence in an economical way in the real world?
Many studies, so intent on showing an effect, invest an inordinate amount of resources–far more than could realistically be deployed in regular clinical practice–in ensuring adherence, only to undermine the applicability of the study to real life.
Yes, DASH-WM produces clinically significant reductions in blood pressure. But does this mean that recommending a patient consume DASH and lose weight will produce the same impact?
The answer to that, according to the overwhelming sum of existing literature, is a resounding no. We know from the authors themselves that the more intensive behavioral support likely caused a substantial proportion of the effect seen. Likewise, many other lifestyle intervention trials show the same thing: behavioral management is the overriding determinant of the adherence to, and therefore success of, lifestyle interventions.
In other words, this trial, while laudable in the health impact, is clinically discordant: it cannot reasonably be applied in a clinical environment without serious protocol modification.
As valuable as this trial is in demonstrating an important if unclear physiological effect of lifestyle on blood pressure, it would be nice if lifestyle intervention clinical trials were designed bearing in mind the real-world clinical circumstances of practicing healthcare professionals. Until that happens, such trials are of dubious clinical application and of questionable relevance to guidelines.
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