Doctors who treat patients with high blood pressure received some assurance Wednesday that their use of new national diagnosis guidelines that lowered the threshold for hypertension will prevent disease and save lives.

A study published in JAMA Cardiology estimates that 340,000 cases of cardiovascular disease and 156,000 deaths would be prevented each year if all hypertension patients achieved the goals of the 2017 guidelines, compared to the older recommendations.

The 2017 guidelines, issued by the American College of Cardiology and the American Heart Association, theoretically added 31 million Americans to the nation’s hypertension tally, the new study showed. However, they don’t say all patients need to take drugs to lower their blood pressure; only 11 million of the newly diagnosed patients would need such medications, while the rest would be advised to watch their blood pressure levels or improve their diet and exercise.

The new guidelines set the threshold for diagnosing hypertension at a blood pressure reading of 130/80 instead of 140/90.

Dr. Michael Miedema, a preventive cardiologist with Allina Health in Minneapolis, said the research is helpful because the 2017 guidelines have created a “gray zone” of patients who aren’t sure what to do about their new hypertension status and whether to take medications to lower their risks of heart attack and stroke.

“Preventive medications have such a different psychology to them,” he said. “I’m never going to have a patient coming in saying to me, ‘I didn’t have a heart attack today. I’m so happy I’m on my blood pressure medication. I can’t wait to take it again tomorrow!’ ”

While three primary classes of medications for managing high blood pressure are well-studied and generally safe, they do carry risks — particularly of causing low blood pressure, which can lead to falls and injuries in the elderly, among other symptoms.

If the 2017 criteria were applied nationwide, the increased use of medications would likely result in 62,000 more cases of abnormally low blood pressure, 32,000 cases of patients fainting, and 79,000 cases of acute kidney injury or renal failure, the study found. But the researchers from Tulane and Northwestern universities concluded that those risks were outweighed by the benefits of addressing blood pressure in all Americans with levels above 130/80.

Still, in conversations between doctors and patients, the right course isn’t always clear cut, said Dr. Dylan Bindman, an Allina Health family physician in Eagan. Just using the term “hypertension” might vary from patient to patient, even if they have comparable blood pressure levels, he said.

“You have to read the patient and kind of get to know what helps them be their healthiest selves,” he said. “Some patients, it can be very helpful to have that label, if you will. It gets them to change their habits or start a medication. But for others, it … can make them anxious, which can raise their blood pressure and it can make the cycle worse.”

Bindman said he generally agrees with the guidelines, though he professed concerns. The American Academy of Family Physicians late last year declined to endorse the new guidelines, saying they relied heavily on a limited number of studies. The federally funded SPRINT study, for example, was halted early in 2015 because it showed such strong advantages of treating more people with hypertension. But it was criticized for failing to weigh drug risks.

Australian researchers last month cited the risk of creating anxiety in millions of people by telling them they have high blood pressure — some of whom might not need to take medication.

Hypertension has been less of a problem in Minnesota, even under the old definition. A recent report by the Robert Wood Johnson Foundation, “State of Obesity,” ranked Minnesota second-lowest nationally in the rate of adults with hypertension — 26.3 percent in 2015. However, that rate has risen from less than 20 percent two decades ago, and minority groups in Minnesota have higher rates.

Dr. Andrew Smith, a cardiologist at the Park Nicollet Heart and Vascular Center in St. Louis Park, said the new guidelines are beneficial. He said they have already motivated some patients to get their blood pressure below 130/80 by taking medications or improving their diet and exercise habits.

The guidelines also offered practical advice for measuring a diagnostic blood pressure accurately, a major concern because some people suffer “white coat hypertension” — elevated pressure just from visiting a clinic.

Ultimately, they have transformed physicians’ hypertension management, from something that a doctor orders to something developed in conversation with patients, Smith said.

Doctors, he said, “have had to turn the reflexive, ‘You have high blood pressure, you get treatment,’ into a conversation with patients.”