So you think your blood pressure is normal? Think again. The latest iteration of an “ideal” blood pressure — a level of 120 millimetres of mercury for systolic pressure, the top number — has been called into question by a long-term multi-ethnic study of otherwise healthy adults.
The study, published in JAMA Cardiology, found that as systolic blood pressure rose above 90mm, the risk of damage to coronary arteries rose along with it. Systolic blood pressure represents the pressure within arteries when the heart pumps. The new findings suggest a need to look more carefully at why, despite considerable overall improvements in risk factors for heart disease in recent decades, it remains a leading killer.
Starting in the 1940s, cardiovascular researchers have unveiled evidence that American society all but guarantees a disproportionately high risk of dying of heart disease. Since my first weeks writing for this newspaper in the early 1960s, I’ve publicised their advice urging people to curb preventable risks to their hearts.
Although significant progress has been made on several fronts, especially drastic cuts in smoking and lowered levels of cholesterol, atherosclerotic heart disease still kills far too many. If not for a plethora of therapeutic advances, such as antihypertensive drugs and open-heart surgery, life expectancy would be a lot worse.
And as shown in the study, even levels of blood pressure that are generally considered “normal” may indeed be high enough to foster the development of atherosclerotic heart disease by more than fourfold.
Heart experts have long known that people in traditional non-industrial societies typically maintain systolic blood pressures in the low 90s throughout life. Their blood pressure does not rise with age. Rather, it seems, the increase in blood pressure that is common for us in late adulthood is an artifact of our sedentary lifestyles and diets rich in calories and high in sodium, all of which result in stiff, narrowed arteries that result in high blood pressure.
The study, directed by Dr Seamus P. Whelton, cardiologist and epidemiologist at the Johns Hopkins Ciccarone Center for the Prevention of Cardiovascular Disease in Baltimore, US, followed a cohort of 1,457 middle-aged men and women, initially free of atherosclerotic vascular disease and known risk factors, for 14.5 years. As the participants aged, their risk factors for heart disease increased, along with calcium deposits in their coronary arteries and cardiovascular events (heart attacks).
The research team focussed on increases in systolic blood pressure with age, adjusting the data for changes in other heart risks. They found that for every 10mm increase in systolic blood pressure, the risk of calcium deposits and heart attacks rose accordingly. Compared to people with systolic pressures of 90 to 99mm, those with pressures of 120 to 129mm were 4.58 times more likely to have experienced a cardiovascular event.
Still, Whelton said that it would be wrong to focus preventive strategies on blood pressure alone. People with high blood pressure, he said, “are also more likely to have higher cholesterol and blood glucose levels. The ideal strategy would focus on all risk factors — blood cholesterol, blood sugar and blood pressure. Maintaining a healthful diet, exercising, not smoking and consuming alcohol in moderation would improve all the risk factors for cardiovascular disease”.
Levels of what doctors consider a healthy systolic blood pressure have been falling for half a century. In August 1950, a report in JAMA suggested that labelling systolic blood pressures of 140, 150 or 160mm as abnormally high is “arbitrary, particularly when age is concerned”. The authors suggested that raising acceptable blood pressure levels for people over 40 “would result in a decrease in the reported incidence of hypertension and thus allay some of the widespread fear regarding high blood pressure”.
The latest blood pressure advisory, issued in 2017 by the American Heart Association and American College of Cardiology, considers a systolic blood pressure of 120mm the upper limit of normal and defines 130mm and above as high blood pressure that warrants treatment with medication.
In an editorial accompanying the new study, Dr Daniel W. Jones, hypertension specialist at the University of Mississippi Medical Center, US, who helped formulate the current blood pressure guidelines, wrote, “the risk imposed by a blood pressure level below the currently defined hypertensive level is continuous beginning with a systolic blood pressure as low as 90mm mercury”.
Jones said, “Normal blood pressure can be in the 90s, which is what it is in young healthy women. Prevention should start with children — with a healthy diet low in salt and regular exercise — and adults should avoid gaining weight with age.”
When I asked why doctors don’t put more emphasis on maintaining youthful levels of blood pressure, Jones said that in the 1960s medical schools taught that blood pressure should rise with age to assure an adequate supply to the brain.
“Only in recent decades has it been accepted that it’s actually better for the brain, kidneys and heart to keep blood pressure down as people age,” he said.
New York Times News Service
