Blood Pressure: How Low Is Just Right?

If up is bad, down must be good. If higher is worse, lower must be better. These statements appear to be logical, but logic does not always rule, at least as far as blood pressure is concerned.

High blood pressure is dangerous, to put it mildly. So lowering it should be good. But how low is low? Back to normal? Or even lower?

Risks of hypertension

Heart attacks, heart failure, strokes, kidney failure: This is a partial list of the devastation that high blood pressure causes every day. Almost a billion people worldwide suffer from it, and have been, for many years. We should have learned how to control this by now, right? Wrong!

Which pressure to control?

Most people are aware that blood pressure (BP) is written as two numbers, written one above the other; for example, 120/80 millimeters of mercury (mm Hg).

The top number is the systolic pressure, generated when the heart muscle contracts to pump blood out to the rest of the body. The bottom number is the diastolic pressure, recorded while the heart muscle relaxes, and fills up with blood again.

It is a matter of age

In people 50 years or older, the commonest form of high BP is an elevation of systolic BP, with the diastolic BP being normal. This is called isolated systolic hypertension.

FYI

Normal BP is now defined as less than 120 mm Hg systolic and less than 80 mm Hg diastolic (<120/80).

Systolic BP matters

In people 50 years or older, the risk of complications of hypertension is more closely linked to the systolic BP compared to the diastolic BP. Thus controlling the systolic BP assumes greater importance in this age group.

What is a risky level of BP?

Good question!

One could feel that since we have defined normal BP as < 120/80 mm Hg, there should be no risk below that.

That would be naive!

Risk is progressive!

A meta-analysis of 61 studies involving 1 million adults was published in the Lancet in 2002: http://goo.gl/QLe3QG.

The results were interesting: Risk keeps rising progressively with increasing systolic BP.

The floor, above which risk increases? 115/75 mm Hg, according to the Lancet article.

So should we lower systolic to 115 mm Hg?

Not so fast! Unless you want to have people keeling over and getting dizzy and collapsing!

So what’s the target?

That’s the million dollar question!

Lots of expert bodies have issued lots of guidelines. Most of which end up being ignored by the doctors in the trenches, who do the real work of treating patients instead of writing guidelines.

But before we even talk about targets, let us look for hard evidence. Does treating high BP reduce risk?

Yes, it does!

Clinical trials show that treating high blood pressure lowers the risk of developing heart failure by up to 64% (http://goo.gl/O50O5p; http://goo.gl/o6a8sT).

Strokes are reduced by 35 to 40%, while heart attacks are reduced by 15-25% just by treating hypertension.

So what’s the problem?

Where to stop, and whom to believe: That is the problem.

And looking for solid evidence.

All doctors know about treating high BP. They are just confused by data, and by so-called experts. When to start treating, what medications to use, and when to call it a day are not easy questions to answer.

The data, please

Randomized, controlled trials are the gold standard as far as medical evidence goes. And most of those in the field of hypertension reveal a benefit of treating systolic blood pressure only to a target of less than 150 mm Hg. Data regarding the benefit of lowering the systolic pressure to even lower targets are rather limited (or were, till recently).

ACCORD study

This trial evaluated more than 4700 patients with type 2 diabetes, to see which systolic BP target was better, less than 140 mm Hg or less than 120 mm Hg.

After a mean follow-up of 4.7 years, there was no significant difference between the two groups regarding the endpoint of fatal or non-fatal major cardiovascular events, such as stroke, heart attack, or death from cardiovascular causes. You can read more about this study here: http://goo.gl/mHxDms.

So where do we stand now?

The common advice is still to lower systolic BP to less than 140 mm Hg in most patients.

There is some debate about this, especially in older patients.

Various guideline-writing bodies have also come out with recommendations which are less than uniform, serving often to confuse doctors and patients.

Shall we SPRINT?

This (the SPRINT trial), of course, is the latest study, which was stopped early in August 2015, because of accumulated findings which were felt to be important enough to stop most parts of this trial.

Lower systolic BP targets?

That was the major finding of the SPRINT study.

The participants (9361 of them) were randomly assigned to two groups. In one group, the target systolic BP with treatment was less than 140 mm Hg, while in the other group, it was less than 120 mm Hg.

The group with the lower BP target had lower rates of fatal and non-fatal major cardiovascular events, and lower rates of death from any cause.

So let’s jump on the bandwagon!

Hold on for a while.

The devil, as they say, is often in the details.

Before adopting the results of any trial into widespread clinical practice, we should exercise due diligence.

The SPRINT study population is not representative of the large pool of general patients with hypertension in the real world. There were, as there usually are in trials, strict criteria regarding which patients would be included, and which excluded, from the study. Obviously, they did not take all comers. In particular, patients with diabetes were excluded from this trial.

The way BP was checked in the trial centers was also standardized, and was quite different from what is done in the real world.

Where do we stand?

• 

  As a doctor, if you see a patient who fits the prototype of a SPRINT trial participant, go ahead and treat them to a lower target.

• For the other patients, exercise caution. Use your best judgment based on the patient’s entire clinical profile, including age and risk factors.
• If you are a patient, or have a friend or loved one who is a patient, discuss the issues raised by the SPRINT trial with your doctor.

Details of SPRINT

Stay tuned! We will outline them in a subsequent post.

Want to know more about BP?

Consider reading my E-Book, “High Blood Pressure: 10 Reasons Your Blood Pressure Is NOT Under Control.”

It is available here: http://goo.gl/t3h2zs.