REGARDS trial challenges assumptions about Stroke Belt

Trial found blacks were more likely to be treated for hypertension but were less likely to have blood pressure under control.

NEW ORLEANS – Hypertension awareness, control and treatment were similar in the South to other parts of the country, suggesting that the high incidence of stroke may be attributed to causes other than hypertension.

George Howard, DrPH, chair of the department of biostatistics at the University of Alabama at Birmingham School of Public Health, said the American Heart Association estimates that about 750,000 strokes occur in the Stroke Belt of the southern states.

“There are lots of theories as to why the stroke belt exists. I’m very fond of saying that we all know why the stroke belt exists; we just all happen to disagree with each other,” Howard said a late- breaking clinical trial session at the American Stroke Association International Stroke Conference 2005.

REGARDS

Howard said the prevailing theory is that increased rates of hypertension cause the increased rates of stroke. The REGARDS (Reasons for Geographic and Racial Differences in Stroke) trial is designed to test that hypothesis. Howard presented data on the first 11,606 patients in a trial that will eventually include 30,000.

REGARDS is a national population-based cohort study of participants aged 45 or older. By design, the cohort will be 50% black, 50% white, 50% male and 50% female. The geographic distribution will draw 20% from the “buckle of the Stroke Belt,” 30% from the remainder of the Stroke Belt and 50% from the rest of the contiguous United States.

Volunteers were recruited after responding to a mailing and participating in a 45-minute phone interview from the University of Alabama. Health care workers then visited the homes of volunteers to assess hypertension awareness, treatment and control.

Awareness of hypertension, defined as a positive self-report, was higher among blacks at 92.8% than among whites at 89.2% (P<.0001). There was no regional difference: 90.6% of participants in Southern states said they were aware they had hypertension compared to 91.2% in non-Southern states (P=.49).

Black participants were significantly more likely to be treated for hypertension than whites (91% vs. 86.7%, P<.0001), but there was no regional difference in treatment. Participants in Southern states reported an 89.1% rate vs. 88.7% in non-Southern states (P=.49).

Although blacks were more likely to be treated for hypertension, they were much less likely to be controlled: 61.7% vs. 70.1% among whites (P<.0001). Geographic control measurements found that control was significantly better in the South at 67.8% than in the non-Southern regions at 64.2% (P=.0039).

“It’s not that Southerners don’t know about their hypertension or that they are poorly treated or that they are not controlled. In fact the trends are in the opposite direction,” Howard said. “The implications of this is it might be very challenging to try to reduce the Stroke Belt discrepancy by improving hypertension treatment and control.”

If not hypertension, what?

Franz Messerli, MD, director of the hypertension program at St. Luke’s-Roosevelt Hospital in New York and section editor of Cardiology Today’s Hypertension and Vascular Disease section, said he was not sure the REGARDS study convincingly made the case that hypertension was not the cause of the stroke belt.

“The aim of the study was to recruit 30,000 patients, exactly half of whom would be African Americans and half of them white, half of them living in the South and half of them living in the North. The authors report that African American patients were less likely to have their hypertension under control than white patients. This may be due to socioeconomic factors, lesser compliance and perhaps also to physician bias regarding how aggressively patients need to be treated.

“Since there are considerably more African Americans living in the South than in the North, the study, with its forced 50/50 racial distribution, will not really give us a clear picture of the true prevalence of uncontrolled hypertension in the South vs. the North. Conversely, if we were able to achieve better blood pressure control in African Americans, we would have a considerably larger impact on stroke reduction in the South than in the North.

“We will also have to consider that the metabolic syndrome, obesity and diabetes are more prevalent in the South than in the North. It is, of course, not only uncontrolled hypertension but the total risk-factor baggage that becomes the major detriment of stroke and heart attack. Uncontrolled hypertension in African Americans and a higher prevalence of endocrine metabolic risk factors are, to my way of thinking, a good enough explanation for the occurrence of the Stroke Belt,” Messerli said. – by Jeremy Moore

For more information:

• Howard G, Prineas RJ, Kellum M, et al. Racial and regional differences in awareness, treatment and control of blood pressure [REGARDS]: a guide for interventions to reduce disparities. Presented at the American Stroke Association International Stroke Conference 2005. February 2-4, 2005. New Orleans.