Blood pressure: Why comparing readings is potentially dangerous

Blood pressure: Why comparing readings is potentially dangerous
A mature adult woman of African descent is at a routine medical check. She is sitting on an examination table in a clinic. The nurse is using a blood pressure gauge to check the patient's blood pressure.

New research shows that significant increases in blood pressure among young adults are associated with an increased risk of middle-aged cardiovascular disease. As a result, doctors might need to reconsider the procedure of combining blood pressure readings to assess if medication is required.

Dr. Yuichiro Yano, Ph.D. — an assistant professor at Duke University for Durham, NC’s Department of Family Medicine and Community Health — is the lead author of the new paper.

Dr. Yano and associates started out with suggestions from the current United States Task Force on Preventive Services and the American College of Cardiology / American Heart Association.

For young adults, these mean that doctors should use an average of several measures of blood pressure over time to diagnose and treat hypertension.

However, some studies have suggested that higher variability in visit-to-visit blood pressure readings is linked to a higher risk of cardiovascular disease— especially in adults over the age of 50.

So, could it be that, in young adulthood, higher variability in blood pressure readings means a higher risk of later lifetime adverse cardiovascular events?

Dr. Yano and team used data from the Production of Coronary Artery Risk in Young Adults Survey to find out.

In total, 3,394 participants from across four US states reported blood pressure levels. The findings of their study will now appear in the JAMA Cardiology journal.

Studying blood pressure spikes

The researchers specifically looked at mean (normal) blood pressure levels, cumulative blood pressure sensitivity, visit-to-visit variability, and average annual blood pressure change.

The participants were 18–30-year-old African American and white adults, all of whom participated in the study between March 1985 and August 2015. During this time, the adults took part in 2, 5, 7, 10, 15, 20, 25, and 30 year follow-up exams.

Nearly 46 percent of the participants were African American, and almost 56 percent were females.

The study’s main focus was on systolic blood pressure, which corresponds to the top number of blood pressure readings. A systeolic reading of mercury (mm Hg) above 130 millimeters appears to be a sign of hypertension.

The participants were, on average, 35 years old at around 10 years into the study. Dr. Yano and colleagues identified the young adults who had exhibited changes in their systolic blood pressure and proceeded to track them over the next 2 decades to investigate a potential connection with cardiovascular disease.

A 15% higher cardiovascular risk

181 people died during the study period and 162 adverse cardiovascular events took place. These included heart disease, heart failure, stroke, transient ischemic attack, and peripheral artery disease stent procedures.

The scientists found that the probability of cardiovascular disease in the next 20 years was 15 percent higher for each blood pressure rise of 3.6 mm Hg at young adulthood.

These findings were independent of normal levels of blood pressure at young adulthood.

“If a[ person] comes in with one reading in December and a significantly lower reading in January, the average could be within the range that would seem natural,” Dr. Yano explains.

“But does that disparity in later life lead to health outcomes? That’s the question that we were trying to answer in this study and it turns out that the answer is yes.

Blood pressure variability matters

Dr Yano goes on to explain that the variability of blood pressure in early adulthood should be considered more by patients and physicians alike. Early detection means a person can make changes in lifestyle to prevent hypertension from developing later on.

“Current guidelines for defining hypertension and evaluating the need for antihypertensive therapies ignore variability in readings of blood pressure,” he says.

“I think there was a belief that variability is a phenomenon of chance, but perhaps this research does not indicate that. It is about variability.’

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