Monday, November 9, 2015

Should we SPRINT to lower blood pressure goals?

- Jennifer Middleton, MD, MPH

Just as we were all adjusting to JNC 8's blood pressure goal recommendations this past December (140/90 for most and 150/90 for adults over 60 without co-morbidities), in September the National Institutes of Health (NIH) issued a press release stating that they were halting SPRINT early due to preliminary findings that the benefits of a systolic blood pressure goal of 120 reduced the risk of cardiovascular events and mortality compared to a systolic blood pressure goal of 140.

SPRINT, the Systolic Blood Pressure Intervention Trial, aimed to prospectively enroll and then follow over 9000 patients during a four- to six-year time period to definitely answer that age-old blood pressure treatment question - how low should we go? Participants were at least 50 years of age, had a systolic blood pressure of at least 130, and had at least one additional risk factor for cardiovascular disease (chronic kidney disease, a Framingham score of at least 15%, and/or age of at least 75 years) but no prior history of cardiovascular disease. Patients with diabetes were excluded. The primary outcomes of interest were incidence of myocardial infarction (MI), acute coronary syndrome (ACS), stroke, heart failure, or cardiovascular death; they examined several other secondary outcome measures as well, including all-cause mortality and worsening chronic kidney disease.

Prior studies examining this question found no benefit for keeping systolic blood pressure under 120 but possible harm from doing so; Dr. Lin has reviewed this evidence base twice on the AFP Community Blog, in 2013 and again earlier this year. (There's also an AFP By Topic on Hypertension if you'd like to read more.) So, if the SPRINT findings are legitimate, significant changes may be quickly coming about blood pressure treatment recommendations, including the possible early retirement of JNC 8. The stakes are high.

Stopping a study early isn't necessarily a bad thing. If it's clear, for example, that one arm of the trial is causing harm, then researchers are ethically obligated to stop the study. Similarly, it can be questionable to continue a study when it's clear one treatment is far superior to the other. But stopping studies early also has risks; for example, a smaller number of participants, and/or a decreased amount of time following them, can skew results to look more impressive than they might otherwise have been.

The NIH has faced significant backlash on social media, but for more than just stopping the study early:

From Health News Review:
The big announcement about these “landmark” results doesn’t actually include any “results” from the SPRINT study. You can search the news release high and low but you’ll find nary a single statistic from the study or a number related to what the researchers found.
From The Incidental Economist:
[T]his is basically the release of conclusions without methods or even results. It hasn’t been peer reviewed. I don’t know the details....Those who conducted and funded the study can’t be the ones to judge its merit. 

From Scientific American:
Doctors and reporters only had the slick NIH press release, which glistened with words such as “landmark” and “life-changing” and provided hype but little substance. It did not emphasize that the findings may only apply to a limited segment of the population...and it did not mention potential risks associated with taking multiple blood pressure drugs...
From the PLOS blog:
If the primary outcome turns out to be rock solid and confirmed in the future, other aspects of the study...are vulnerable to the shorter intervention period. That includes knowledge about longer term and less common adverse events, and the impact on subgroups of sicker people.

When it comes to data release of clinical trial results, the NIH should set the standards. It shouldn’t be moving the bar. In this case, one could imagine some overly pushy drug company using this data release to justify releasing more data on its own product. That leads us even further into a world where science is conducted by press release. That shouldn’t be an outcome anyone wants.
Your patients may already be reading and asking about SPRINT; how are you responding? What do you want to see from SPRINT before considering a change in how you manage patients with high blood pressure?

SPRINT was just published today, and no doubt there will be a lot of discussion in the coming weeks dissecting its findings. Watch for more on this topic from the AFP Community Blog, too!