Can Your Blood Pressure Be Too Low? You bet.

You probably haven’t heard much about the dangers of low blood pressure.

In Dr. H. Gilbert Welch’s book Overdiagnosed, he tells the story of a patient of his at the Department of Veterans Affairs (VA) in Vermont. Mr. Bailey was 82 and lived alone on a farm. He worked outdoors almost all day, every day, doing everything from rebuilding stone walls to clearing brush and shoveling snow. He was a healthy man with only a few minor health issues.

But Mr. Bailey ended up on a master list of VA patients with high blood pressure. His systolic blood pressure (the top number) was 160, which is considered high, although his diastolic pressure (the bottom number) was fine, running 70-90.

Seeing that Mr. Bailey was highlighted as someone with a high systolic blood pressure spurred Dr. Welch to start Mr. Bailey on a daily 25 milligram pill of hydrochlorothiazide, a diuretic that reduces the amount of fluid in the blood vessels, and thus lowers blood pressure. It worked. Mr. Bailey’s systolic blood pressure went down.

But then one day Mr. Bailey collapsed. He was working outside on a hot, humid day, got dehydrated, and his blood pressure got too low.

It turns out that when hypertension is moderate, the value of treatment is low, says Dr. Welch. The chance of “overdiagnosis” is  high and the benefit is not worth the risk.

So Mr. Bailey decided to stop taking the pill to reduce his blood pressure.

Lower Blood Pressure May Not Work for Everyone

A study published in JAMA Internal Medicine last year found that older adults who had a systolic blood pressure of 128 or less had a higher level of mental decline than did those with a higher reading. And low blood pressure has been associated with other health issues: studies have  found that lower blood pressure in seniors can cause or be related to declining kidney function.

Scientists aren’t certain why this is true, but basic physics helps answer the question. As we age, our blood vessels  naturally stiffen and may narrow, and either or both of those features can increase blood pressure. If you don’t get enough blood pressure, your vital organs, such as the brain and kidneys, for example, may not get the oxygen they need.

Even in younger people, low blood pressure can be a problem. Anyone of any age who gets dehydrated (causing less “total fluid” in the blood vessels), may get dizzy and even faint.

Confusing Standards 

But it can be confusing to know what’s right to do. Our healthcare system tends to treat blood pressure somewhat aggressively. Just last November, a study and editorial published in the New England Journal of Medicine suggested that a target systolic blood pressure of 120 may be smart.

The study, the Systolic Blood Pressure Intervention Trial (SPRINT), involved almost 1,000 people 50 or older with a systolic blood pressure of 130 to 180. But all the participants in the study already had at least one risk factor for heart disease, such as high cholesterol  or smoking.

Half were in a group aiming for a systolic blood pressure of 120 while the others were going for a blood pressure 140 or lower. All the participants were put on common blood pressure medications. After four years, the ones seeking the 120 systolic blood pressure had a 25 percent lower risk of stroke, heart attack and related problems, including death.

But the trial also showed that people trying for the lower systolic blood pressure number had a higher risk of fainting and reduced kidney function.

Most of those who got their blood pressure down near the 120 blood pressure target had to take three to five medications to do it, while those who were  trying for 140 systolic only had to take an average of one medication. Some patients had to take several drugs to get their blood pressure down to the target, each with its own side effect.

By the way, guess how many different drugs are marketed in the U.S. to reduce high blood pressure? I took a quick look and counted 80, from Accupril to Ziac.  On the positive side, patients and physicians have a wide range of options to choose from. On the other hand, pharmaceutical companies have a big investment in blood pressure management.

Drugs Are Not the Only Way to Achieve a Healthy Blood Pressure

Are there other steps you can take? Exercise moderately for at least 30 minutes five times a week; achieve a healthy weight; cut back on processed and other salty foods; eat plenty of fish,  fresh fruits and vegetables; and limit your alcohol intake.

What Next?

  • Talk with your physician about how your unique combination of characteristics — age, family history, gender, any conditions such as diabetes or kidney disease, cardiac risk factors,smoking habits, stress and lifestyle — should inform your decision about aiming for a a particular target blood pressure.
  • Don’t stop taking any prescribed medications, including any blood pressure medications, without talking with your physician first.
  • If you faint or fall, are dizzy or light-headed, or feel confused or disoriented, or have any other troubling symptoms, contact your physician right away.
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About Barbara Bronson Gray, RN, MN

I'm an experienced healthcare and science editor and journalist. But most of all, I'm a registered nurse with many years of experience working in hospitals. I've learned what patients and families need first hand. But I've also worked to improve hospitals and educate people about their health. I'm committed to helping people take charge of their health care and get what they need from a complex and often discouraging healthcare system.
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