Effectiveness of Blood Pressure Medications Lower in Stroke Belt
Four out of six common blood pressure medicines are less effective for patients who live in the south-eastern region of the United States, an area known to have a higher rate of strokes, than they are for residents outside the area, a new study shows. High blood pressure is the main cause of strokes.
Dr. William C. Cushman of the Veterans Affairs Medical Center in Memphis, Tenn., and colleagues reported their findings in the March 27 Archives of Internal Medicine. The Department of Veterans Affairs Cooperative Studies Program in Washington, D.C. coordinated the randomized, controlled multi-center study.
Just why the medication does not work as well in this region, called the Stroke Belt, remains unclear. However, “age, race, salt intake, excess alcohol intake, and use of non-steroidal anti-inflammatory drugs are recognized as some of the causes of resistance to antihypertensive (blood pressure) medications,” explained Dr. Cushman.
“…we suggest that environmental or other factors may contribute to both the higher stroke mortality and resistance to antihypertensive medications observed in patients residing inside the Stroke Belt,” the authors write.
The decreased effectiveness of medications is not the primary cause of the high death rates from stroke in that region, since strokes have been unusually common there for at least 50 years – long before the widespread treatment of hypertension, the team asserts.
The researchers studied 1,292 men from 15 United States Veterans Affairs medical centers who had diastolic blood pressure between 95 and 109 mm Hg. They measured the patients’ blood pressure, heart rate, weight, height, and did other tests that assessed the participants’ dietary intake of sodium and potassium, their kidney function, and their risk for diabetes, among other factors.
They prescribed for the patients one of the following blood pressure medications: hydrochlorothiazide (Microzide), atenolol (Tenormin), sustained release diltiazem hydrochloride (Tiazac), captopril (Capoten), prazosin hydrochloride (Minipress), clonidine (Catapres), or a placebo. The team classified patients from Dallas and Houston, Tex.; Jackson, Miss.; Memphis, Tenn.; St. Louis, Mo.; and Washington, DC, as living inside or at the periphery of the Stroke Belt; and patients from Allen Park, Mich.; Boston, Mass.; East Orange, NJ; Manhattan, NY; Miami, Fla.; Milwaukee, Wis.; San Francisco, Calif.; San Juan, Puerto Rico; and Topeka, Kan., as residing outside the Stroke Belt. The researchers discovered that after one year, only prazosin and diltiazem were equally effective in all geographic areas. Patients inside the Stroke Belt achieved significantly lower treatment success rates of diastolic blood pressure control at one year with hydrochlorothiazide (63% vs 41%), atenolol (62% vs 46%), captopril (60% vs 30%), and clonidine (69% vs 43%); there were no differences in treatment success rates with diltiazem (70% vs 71%) or prazosin (54% vs 53%).
African Americans responded best to diltiazem and the least well to atenolol and prazosin, the team reports. However, after the team controlled for various patient characteristics, such as weight, heart rate, medication adherence rates, and others, the effect of residing inside the Stroke Belt was significant only for captopril and clonidine, and was somewhat significant for hydrochlorothiazide.
“From a practical management perspective, it can be expected that both black and white patients with hypertension in the Stroke Belt will often require more or different antihypertensive medications, more aggressive lifestyle changes, or both to reach recommended goals for blood pressure compared with patients residing outside the Stroke Belt,” the team writes.
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