Drug-Resistant High Blood Pressure on the Rise

By BRENDA GOODMAN

High blood pressure, the most commonly diagnosed condition in the United States, is becoming increasingly resistant to drugs that lower it, according to a panel of experts assembled by the American Heart Association.

“It’s becoming more difficult to treat and it’s requiring more and more medications to do so,” said the panel chairman, Dr. David A. Calhoun, a hypertension specialist at the University of Alabama at Birmingham.

The problem is not that the medications have stopped working, said the report, published this month in the journal Hypertension. Instead, many blood-pressure patients are sicker to begin with and require more drugs, at greater dosages, to manage their conditions.

The doctors say this is especially worrisome because recent surveys estimate that one in three Americans have hypertension, an underlying cause of heart attacks, strokes, kidney disease and heart failure.

Starting at a blood pressure of 115/80, research shows that the risk of a heart attack or stroke doubles with every 20-point increase of systolic pressure, the top number, or 10-point increase of diastolic pressure, the bottom number.

“High blood pressure is currently the biggest single contributor to death around the world because it is so common,” said Dr. Neil R. Poulter of the International Center for Circulatory Health at Imperial College London. In the United States, it is particularly common among blacks, with 41 percent found to have it in a 2005 study, compared with 27 percent of whites.

Resistant hypertension is defined as blood pressure that remains above clinical goals, even after a patient has been put on three or more different classes of medications. Additionally, patients whose blood pressure can be lowered to normal on four or more drugs should be considered resistant and should be closely monitored, the panel said.

After reviewing the available research on drug-resistant hypertension, a phenomenon first described in the 1970s, the panel found that it became more likely with advanced age, weight gain, a diet high in sodium, sleep apnea or chronic kidney disease.

Living in the Southeast, a region long recognized as the “stroke belt” of the United States, is also a risk factor for blacks and whites, though researchers are not sure why. An author of the new paper, Dr. William C. Cushman, chief of preventive medicine at the Veterans Affairs Medical Center in Memphis, said he suspected factors like inactivity, obesity and diets high in salt and fat.

Pat J. Dixon, 58, a nurse in Atlanta, takes five medications to lower her blood pressure. In many ways, Ms. Dixon is typical of a patient who develops resistant hypertension. At 5 feet and 172 pounds, she is obese, and her weight gain has caused mild Type 2 diabetes, for which she takes yet another drug. The diabetes is an extra strain on the kidneys, in turn worsening her blood pressure.

Ms. Dixon said that she did not use much salt when she cooked but that she did like to snack on potato chips.

“My doctor tells me about every week that I’m going to eat myself to death,” she said. “You do kind of get worn out and depressed every morning that you have to take five or six pills.”

The new report is one of the first to help doctors recognize and manage this growing group of difficult cases. Because so few studies have focused on resistance, the authors say, the number of drug-resistant patients is unclear.

By reviewing studies of patients with at least some hypertension, the panel estimated that 20 to 30 percent could not control their blood pressure with three or more drugs, even when taking them exactly as prescribed. The 20 to 30 percent cohort appears to be growing. A large study in 2006 from Stanford found that the number of blood-pressure patients who were prescribed three or more drugs had increased over 12 years, to 24 percent from 14 percent.

If patients need that many drugs, experts say, they are likely to be at greater risk for illness even if they lower their blood pressure to normal. These patients have usually had high blood pressure for some time and, as a result, have more organ damage.

“It’s a critically important issue,” said Dr. Sheldon Hirsch, chief of nephrology at Michael Reese Hospital in Chicago. “One of the biggest failings in medicine is that as we increasingly realize the importance of treating hypertension, that lower numbers are better than higher numbers, we have increasing trouble reaching those goals.”

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