Blog | Wednesday, June 26, 2013

Are we over-treating high blood pressure?

JAMA Internal Medicine released an opinion piece that is sure to start some fights. In it, Iona Heath, a retired, well-regarded general practitioner in the UK argues that we are over-treating mild high blood pressure. To understand her arguments, we have to dig a bit into what we know.

Hypertension affects about a third of American adults. Most Americans who have heart attacks, strokes, or heart failure have hypertension. It's estimated that high blood pressure contributes to over a third of a million deaths yearly in the U.S. It's also under-treated, with fewer than half of hypertensive patients having their condition under control.

But it's more complex than that. We divide treatment of blood pressure into primary prevention and secondary prevention. Secondary prevention is simple: once you have had a hypertension-related problem such as heart attack or stroke, the statistics clearly show that tight control of blood pressure prevents another event. Anyone who argues otherwise is, in my opinion, out of their mind.

Primary prevention is a bit murkier, and the subject of Dr. Heath's article. The idea is that by treating high blood pressure before the heart attack (or stroke, or kidney failure, etc.) we can prevent these from happening in the first place. There is little debate about this, but over the years there have been vigorous discussions about what levels of blood pressure to treat. In the U.S. we often rely on the Joint National Commission, a panel of experts who review the data every few years and make recommendations.

The current recommendations are based on decades of evidence that shows the risk of heart disease doubles with each increase of 20 mm Hg to the systolic blood pressure (the top number). In people who do not have other risk factors for heart disease, the goal is to keep the blood pressure under 140/90.

Heath argues that this is too aggressive, and that we over-treat people whose blood pressures run in the 140-160/90s range. She bases her opinion on a recent review published by the Cochrane Collaboration, an evidence-based medicine group that keeps an eye on such things. The review included data from four studies (they use fairly strict selection criteria).

Cochrane's conclusions were fairly clear: When data from the four studies were analyzed, the treatment of mild hypertension did not prevent important outcomes such as heart attack and stroke, but did cause side-effects.

At what level to treat high blood pressure is a hugely important question, given its impact on the nation's health. As I said above, we're talking about people who don't already have other heart risks, and we're talking about whether or not to commit them to long-term treatment. We're also talking about patients who have not been able to bring their pressures down through proper diet and exercise (which, unfortunately, is a whole lot of people).

So what evidence is there to treat so-called low risk people with mild high blood pressure?

The World Health Organization and the JNC both recommend an aggressive approach to treating high blood pressure, even in so-called "low-risk" patients. They do this for a variety of reasons, including some pretty compelling data. Heart and kidney risk rises with blood pressure: there is no "safe" level of high blood pressure. In patients with other risks, the benefit is clear, but what about low-risk patients? Given that many if not all of them will progress with age, and that heart and kidney damage is cumulative, it seems unwise to wait until they either get very high or develop a complication of their hypertension.

It's not that the evidence is conclusive; the Cochrane report reminds us that there may be hazards and costs to treating those with lowest risk, which, statistically, is nearly a tautology. Of course those with less risk will show less immediate benefit. The real question, one which is difficult to study due to ethical considerations, is how much are we helping our mildly hypertensive patients by lowering their numbers.

One Cochrane report combining four studies is not about to change the way most of us practice medicine. Given the disease burden caused by high blood pressure, none of us should rush to raise our treatment thresholds. While Dr. Heath raises some interesting points, her call for significantly raising the treatment threshold (to 160/100) should be discarded until stronger evidence supports her ideas.

Peter A. Lipson, ACP Member, is a practicing internist and teaching physician in Southeast Michigan. After graduating from Rush Medical College in Chicago, he completed his internal medicine residency at Northwestern Memorial Hospital. This post first appeared at his blog at Forbes. His blog, which has been around in various forms since 2007, offers "musings on the intersection of science, medicine, and culture." His writing focuses on the difference between science-based medicine and "everything else," but also speaks to the day-to-day practice of medicine, fatherhood, and whatever else migrates from his head to his keyboard.