WEDNESDAY, Jan. 22, 2020 (HealthDay News) -- If your blood pressure numbers swing from low to high and back again in your 20s, that could bode ill for heart health in middle age, new research shows.

In fact, every 4 mm Hg spike in systolic blood pressure -- the top number in a reading -- during young adulthood was tied to a 15% higher risk for heart disease in midlife, the research team found.

Study lead author Dr. Yuichiro Yano believes the findings have implications for how routine blood pressure checks are interpreted by doctors.

"If a patient comes in with one reading in December and a significantly lower reading in January, the average might be within the range that would appear normal," said Yano, an assistant professor of family medicine at Duke University in Durham, N.C.

"But is that difference associated with health outcomes in later life?" he said in a Duke news release. "That's the question we sought to answer in this study, and it turns out the answer is yes."

In their study, the researchers gathered data on nearly 3,400 people who enrolled in a heart disease study in the mid-1980s.

The patients' blood pressure was taken several times over the following 10 years, and after a decade the patients averaged about 35 years of age.

By then, researchers identified which patients had variations in systolic blood pressure and then tracked their heart conditions for another 20 years, when they averaged 55 years of age.

Over those years, 181 participants died and 162 had cardiovascular illness or events such as heart disease, heart failure, stroke, mini-stroke, or a stent placed to unblock arteries.

The Duke team found that blood pressure fluctuations in youth did seem correlated with higher odds for heart trouble decades later. That finding held even when the researchers factored in a patient's average blood pressure during young adulthood.

Current guidelines that direct doctors on whether or not to prescribe blood pressure medicines "ignore variability in blood pressure readings," according to Yano.

"I think there has been a belief that variability is a chance phenomenon," he said, "but this research indicates maybe not. Variability matters."

Two cardiologists unconnected to the new research agreed that yo-yo blood pressure numbers could be worth watching.

Dr. Guy Mintz directs cardiovascular health at the Sandra Atlas Bass Heart Hospital in Manhasset, N.Y. He said that younger patients, especially, often downplay spikes in blood pressure.

"Many patients come into the office and are found to have an elevated blood pressure, but before the doctor can say hypertension, the patients have their script: 'I had coffee this morning, I rushed here, I was aggravated at work or I had ethnic salty food last night,'" Mintz said.

But "the message from this study is powerful and important," he said. "Clinicians cannot accept patient excuses, and must be more vigilant in treating hypertension at an earlier age."

Those treatment aren't just medications, Mintz added, but include lifestyle changes such as cutting back on salt, losing excess pounds and getting into an aerobic exercise routine.

"Only when lifestyle intervention does not get the patient to the blood pressure goal should medication be considered," Mintz said.

Dr. Satjit Bhusri is a cardiologist at Lenox Hill Hospital in New York City. Reading over the findings, he said there are physiological reasons why swings in blood pressure could speed heart disease.

"When blood pressures swing from very high to very low, our organs are not able to respond and function in a steady state," Bhusri explained. "As a result they harden, the arteries stiffen, and the heart muscle can even fail. It is as if a fire hose is turning on and shutting off repeatedly."

The report was published online Jan. 22 in the journal JAMA Cardiology.

More information

For more on blood pressure, see the American Heart Association.