Can Treatment Lower Your Blood Pressure Too Much?

The Hypertension "J Curve"

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“My doctor started treating me for high blood pressure six months ago, and my readings went from 155/90 down to 120/70, which I thought was wonderful. So last week I was quite surprised when my doctor expressed concern that she had pushed my blood pressure too low, and dropped my dose of blood pressure medicine. My question is: What the heck? Too low? Is this really a thing, or should I find myself a new doctor?” - Sidney from Oregon

As it happens, Sidney, your doctor appears to be up to date on the latest evidence regarding the therapy of hypertension. There’s at least some indication that a blood pressure which would be considered great in an untreated person (120/70 for instance), might be too low for a person on blood pressure treatment.

Hypertension, or high blood pressure, is a very common medical condition that, if untreated, can lead to myocardial infarction (heart attack), heart failure, stroke, and kidney disease. If you have hypertension it is important that you and your doctor take the steps necessary to adequately lower your blood pressure, before irreversible damage is done to your heart, brain or kidneys.

That part of the equation is clear. The controversy lies in how far the treatment of hypertension ought to be pushed.

What Are The Right Treatment Goals?

For many years, experts in hypertension were fond of saying, “When it comes to blood pressure, the lower the better.” This statement was always something of an exaggeration, since reducing the blood pressure to very low levels, obviously, can lead to lightheadedness or even syncope. But given that broad limitation, “the lower the better” seemed to be a reasonable approach, because in the general population it is essentially true - the lower the blood pressure, the lower the risk of cardiovascular or kidney disease.

It has simply been assumed that the same rule should apply to hypertensive patients on treatment. After all, countless studies have shown that when you reduce the blood pressure in patients who have hypertension, their outcomes significantly improve. So doctors felt comfortable reducing their blood pressures as much as they could, as long as their patients were not having symptoms of lightheadedness or orthostasis.

This is why most hypertension treatment goals are expressed as a “lower than” value (such as, systolic blood pressure lower than 140 mm Hg), instead of as a range of values (such as, systolic pressure between 130 - 140 mm Hg).

It has only been in recent years that this “the lower the better” paradigm has come under serious question. It now appears that it may be possible to reduce the blood pressure below an optimal value, and potentially to produce harm in doing so.

The Blood Pressure “J Curve”

Some recent studies have suggested that clinical outcomes in patients treated for hypertension may follow a “J curve,” where outcomes appear to be optimal within a particular range of blood pressures. If the blood pressure while on treatment is either above or below that optimal range, clinical outcomes become worse. If the J curve hypothesis is real, then the “lower is better” paradigm is false - and doctors will need to be more careful about just how far they reduce their patients’ blood pressures.

One of the more important studies making this point was published in 2014 in the Journal of the American College of Cardiology. Researchers from the Southern California Kaiser Group identified nearly a half million patients who were treated for hypertension, and compared their blood pressures on treatment to their clinical outcomes. They found that the optimal systolic blood pressure while on treatment was between 130 - 139 mm Hg, and the optimal diastolic blood pressure was between 60 - 79 mm Hg. On-treatment blood pressures that were either above or below these ranges were associated with worse outcomes.

The J curve idea may be especially important, and is now widely accepted, in older patients who have isolated systolic hypertension. Some recent guidelines urge caution in pushing the blood pressure too low in these patients, and most doctors are now quite careful about treating their elderly hypertensive patients too aggressively.

Still, it should be noted that several studies have failed to identify a J curve for non-elderly patients being treated for hypertension, and the question remains somewhat controversial among experts. But most experts have become a lot more circumspect in expressing the “lower is better” idea, and more and more experts are coming to accept that the J curve is real.

So, Sidney, your doctor’s recommendation to back off on your hypertension therapy is consistent with the latest evidence. We will just have to wait and see if the expert panels which manufacture the treatment guidelines will eventually catch up with her.

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Article Sources
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