The National Heart, Lung, and Blood Institute announced that is was stopping the SPRINT (Systolic Blood Pressure Intervention Trial) study early because the early results so emphatically showed that getting the systolic blood pressure (the top number, reflecting the arterial pressure when the heart is squeezing) to 120 or below saved lives.
We've known for half a century that blood pressure below 140/90 reduced heart attacks, strokes, and kidney disease. The SPRINT study was designed to address the question, “How low should we go?”
Apparently, lower than we'd thought.
What's elegant about this study is that it's a randomized controlled trial. This is the best kind of study, which compares groups, one doing the “usual thing” with an intervention arm, in this case the group receiving medication to lower their systolic blood pressure to 120 or below. More than 9000 people were part of the study, and all of the participants were aged 50 or older, which means that the study has oomph. Its results will have real-world applicability.
The study directors found such a significant reduction in the number of strokes, heart attacks, and deaths expected in a population that size in only 3 years that they felt it was ethically imperative to stop the study early to share the preliminary results as they are sure to change medical practice. When that happens, it is big news.
The results have yet to be published in a medical journal, which will take a few months. When that happens, we can more carefully examine what was done and draw more definitive inferences from the research.
Until then, I wonder, how low is too low for blood pressure?
And what about the folks at the older end of the spectrum? Doctors that care for older folks know that there is some inflection point at which physiology changes enough so that pushing down blood pressures and cholesterol numbers becomes counterproductive.
We will need more research to understand when it's right to back off on aggressive cardiovascular risk factor treatment. We don't want to medicate people to the point that they fall down and break their hips. We pledged to do no harm.
This post by John H. Schumann, MD, FACP, originally appeared at GlassHospital. Dr. Schumann is a general internist. His blog, GlassHospital, seeks to bring transparency to medical practice and to improve the patient experience.