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Why Does the Definition of “Normal” Blood Pressure Keep Changing?

I’m sure a lot of people have had similar experiences at the doctor’s office: Someone takes my blood pressure and says it’s a little high. They ask if I’ve had any coffee that day (of course) and whether I’m nervous (not especially). They tell me that because I’m young and not overweight, my high reading is a bit perplexing. Then they chalk it up to “white coat syndrome” and mark the numbers on my chart.

At first, I was surprised by nurses’ nonchalance toward my high BP. But it’s probably too common an issue to faze them, considering that just under half of Americans now have hypertension, the clinical term for high blood pressure. This is partly because rates of obesity and diabetes, two conditions commonly associated with high blood pressure, continue to rise. But it’s also because the “normal” range for blood pressure keeps dropping. In 2017, the American Medical Association, the American College of Cardiology and the American Heart Association revised the guidelines for diagnosing hypertension. As a result, 46 percent of Americans now fall into the high BP range.

Every time your heart beats, it creates pressure (blood pressure) that pushes blood through blood vessels, namely the arteries, which carry blood away from the heart to other parts of the body. A blood pressure reading tells us how forcefully blood is being pushed against the artery walls. Over time, hypertension can damage the arteries and lead to cardiovascular disease.

There are two types of pressure, which is why a blood pressure reading has two numbers: The top number, systolic pressure, indicates the amount of arterial pressure exerted when the heart beats. A systolic reading in the 120 to 129 range is considered elevated; normal means under 120. The lower bottom number, diastolic pressure, indicates pressure exerted between beats, when the heart is resting.

Whether systolic or diastolic pressure is a more meaningful measure of cardiovascular health has been a topic of debate for years. While systolic blood pressure tends to command more attention, health experts currently say both numbers matter.

For years, hypertension was defined as a systolic reading of 140mmHg or higher, meaning at least 140 millimeters of mercury. Now, the cutoff for stage 1 hypertension is 130mmHg. But some wonder if frequent revisions of blood pressure guidelines ultimately do more to sow confusion than save lives. More people with elevated and high blood pressure means more people taking pills to control it — and at younger ages — than ever before, which worries some health experts. It worries me too: Even though I feel fine (most people with even very high blood pressure don’t experience any symptoms), I’ve taken a blood pressure pill for more than a decade, since I was told I had prehypertension, also called elevated blood pressure, at 30 years old. Lately I’ve been wondering whether there are any drawbacks to taking my medication on a long-term basis.

“That’s where some of the controversy and debate has come from,” says Faisal Rahman, a blood pressure researcher and cardiology fellow at Johns Hopkins Hospital. “As the range considered healthy keeps getting lower and lower, people ask whether we should be medicating so much of the population and what the benefits and risks are.”

The publication of the National Institutes of Health Systolic Blood Pressure Intervention Trial (known as SPRINT) in November 2017 has a lot to do with the lower blood pressure guidelines. Researchers followed more than 9,000 participants 50 and older who had both systolic blood pressure of 130 or higher and at least one other risk factor for heart disease. They concluded that getting participants’ systolic blood pressure down below 120 reduced cardiovascular events such as strokes by 25 percent and reduced the risk of death by 27 percent. Impressive findings, but some experts say they’re concerned that a new threshold was set a little too quickly.

We still don’t have a solid reason to assume that when it comes to blood pressure, lower numbers mean better health.

“We generally don’t change medical guidelines based on a single study, yet that was done in the case of the SPRINT investigation,” says Dr. Stephen A. Martin, a doctor of family medicine and associate professor at the University of Massachusetts Medical School. “SPRINT measured blood pressure in an unusual way that we don’t use in practice, and likely made the blood pressures look lower than they would in a regular health care setting.”

In addition, SPRINT participants were older and at higher risk for heart disease than the average patient with the same blood pressure numbers, he says. Martin also points out that a study published in December 2018 found that treating low-risk patients for mild hypertension did more harm than good. 

In fact, the concept of prehypertension (now called elevated blood pressure) only first came up in 2003, notes Dr. Linda Lee, a cardiologist and clinical associate professor at the University of Iowa Carver College of Medicine.

“I think the point was to say that prehypertension is not benign and to bring attention to the issue,” Lee says. “But they didn’t say, ‘We must treat this,’ and that not treating it is a disservice to the patient.”

How low to go?

In the 1970s, the rule of thumb for doctors was that as long as blood pressure wasn’t higher than the patient’s age plus 100, they were fine. When early studies on the effects of high blood pressure were published 50 years ago, Rahman explains, researchers were just trying to get subjects’ blood pressure below 160.

“But it wasn’t clear how much lower would be beneficial,” he says. Bringing blood pressure down too low can cause dizziness and lightheadedness, which puts older people at risk for falls. And some data suggests pushing diastolic blood pressure (the lower number in a reading) too low might actually increase the risk for heart attacks.

“If you start out at 160 and are treated for high blood pressure, there seems to be an increase in risk of death when you go below 120,” says Dr. Michael Hultström, a kidney physiologist and associate professor of physiology and intensive care medicine at Uppsala University in Sweden.

In other words, we still don’t have a solid reason to assume that when it comes to blood pressure, lower numbers mean better health. And continually moving the goalpost for what’s considered “normal” can throw patients for a loop.

“Patients think, ‘First you tell me my blood pressure is high when it’s 150/90, then it’s high at 140/85, and every time I get to the benchmark, you tell me I need more pills,” Lee says. “Then they’re more resistant to their treatment.”

The stakes are high

There are plenty of reasons to err on the side of caution when it comes to controlling blood pressure. For one thing, high blood pressure is the No. 1 cause of strokes, which occur when a blood vessel to the brain is blocked by a clot or ruptures in a hemorrhage. In addition to stroke risk, high blood pressure is thought to raise the risk for heart disease, kidney and eye diseases, aneurysms and dementia.

Many people underestimate their risk: In May, researchers at Johns Hopkins Medicine published a study evaluating data from 6,800 people who considered themselves healthy and found that 10 percent showed evidence of heart disease. Another recent study concluded that the incidence of strokes has increased significantly among people 18 to 34 years old. In a 2011 paper, researchers noted an increase in stroke-related hospitalizations since mid-1990s. The uptick emerged across gender lines, but was most pronounced in young and middle-aged men. Stroke risk is especially high for African Americans, who are twice as likely as whites to experience a stroke and to die from one. After director John Singleton died of a stroke in April at 51, his family implored black men to get their blood pressure in check to protect themselves.

My doctor suggested I go off my blood pressure pill for a while to see if I could manage things through lifestyle changes. I started exercising more and cut down on salt and alcohol. Heavy drinking, meaning more than one drink a day for women or two for men, can spike blood pressure, but it’s not considered a major factor. After instituting my health kick, I assumed my blood pressure would drop. Instead, it was worse than I’d ever seen it: in the 170s on the first systolic reading and in the 150s the second time. My doctor put me back on my pill.

Throughout my 30s, I joked about my blood pressure medication, referring to it as my “old people pill.”

Because the health damages of high blood pressure can be insidious, it’s important to get it under control. “It’s difficult to quantify the damage happening internally unless you have an adverse event such as a stroke,” Rahman notes. But Lee says it’s a mistake to use the same numerical guidelines to assess blood pressure in all patients. Different patients have different levels of risk for cardiovascular disease, and target BP ranges should reflect that.

Race and family history are two well-established risk factors. So are cholesterol, kidney disease, diabetes, obesity, a sedentary lifestyle and smoking. Lifestyle changes to mitigate these risk factors are the first-line treatment for high blood pressure, depending on how high the number is, says Dr. Nieca Goldberg, clinical associate professor of medicine at the New York University School of Medicine and co-medical director of the 92nd Street Y’s Cardio Rehab Program.

When necessary, she says, there are many blood pressure medications with good safety records — and the list of available, recommended drugs keeps changing. “Most people are on two or more, the reason being is that we get more efficient control targeting different mechanisms,” Goldberg says.

It makes sense to use multiple drugs at the same time, Hultström explains, because blood pressure is regulated by a number of hormonal systems in the body, so “when you need to lower blood pressure a lot, you basically inhibit those systems more and more, as well as inhibit more of them, which is why you might need to take several drugs.”

On the patient end, make sure you know your family history regarding diabetes, stroke and heart disease so your healthcare provider can accurately assess your risk. Don’t wave off physician recommendations to lose weight or get more exercise. And make sure you understand what “cutting down on salt” in your diet actually looks like. A common directive is to consume no more than 2,300 milligrams of sodium a day, which is less than the amount in a teaspoon of table salt.

If you use an at-home blood pressure monitor, bring it to your appointments to make sure you’re using it correctly. Lee says she once discovered that one of her patients was taking his blood pressure while holding his arm high over his head, which gave him lower but wildly inaccurate reading.

Most importantly, if your doctor tells you your blood pressure is high or elevated, don’t just hope for the best and ignore the warning. I can appreciate the urge to shrug it off. Throughout my 30s, I joked about my blood pressure medication, referring to it as my “old people pill.” During my brief break from Lisinopril, it felt freeing not to take a daily pill. One less thing to remember and worry about.

Then I got a BP reading approaching hypertensive crisis level, despite feeling perfectly healthy. The fact that I had no indication of the problem, and no reliable way to sense it on my own, left me shaken. Now, easing into my 40s, I’m taking blood pressure control a lot more seriously. And I’m taking my old people pill without grumbling.

Show Comments (4)

    I control high blood pressure with diet.

  2. Denise R Jackson

    Excellent, well-written and timely article. After being prescribed a calcium channel blockers for my elevated blood pressure recently, I’ve decided to go with diet and exercise instead, as the medication has made a minimal difference in my readings.
    Thank you.

  3. Jack

    I do regular exercise, try decreasing my anxiety,
    and lessened the sugar quantity, and now my blood
    pressure has lowered and I am getting normal.
    Thanks by Newz Hub

  4. Pete Smith

    The only thing I can say is as with most things, “follow the money”! Drugs of all types are a BIG business in this country. The companies can’t make any money if they are not “sold”. Not to say that we are a very unhealthy population given the easy access to fast and prepared foods!

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