High BP not causing Stroke Belt

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High BP not causing Stroke Belt
February 9, 2005

New Orleans, LA - First data from a new US-wide epidemiological study of stroke have turned up a surprising finding, the fact that the higher rate of stroke death known to occur in the Southern states--known as the "Stroke Belt"--may not be just due to hypertension.

Statistician Dr George Howard (University of Alabama at Birmingham) reported the first results from the Racial and Regional Differences in Awareness, Treatment, and Control of Blood Pressure (REGARDS) study during a late-breaking session at the American Stroke Association International Stroke Conference last week.

The study shows that, contrary to popular belief, those in the South are as aware of hypertension and as likely to be receiving treatment as people elsewhere in the US. Also, they were more likely to have their hypertension controlled than those living in non-Southern states.

Differences in awareness, treatment, and control of hypertension between Southerners and non-Southerners









Hypertension awareness, treatment, and control
Southerners (%)
Non-Southerners (%)
p
Awareness
90.6
91.2
0.49
Treatment
89.1
88.7
0.49
Control
67.8
64.2
0.0039











All of this indicates that "hypertension is probably not what's causing this," Howard told heartwire . "If we think we can eliminate the Stroke Belt through hypertension control, that's not going to happen." He says there are many other theories about what may be contributing to the excess stroke mortality seen in the Southern states--which is about 40% to 60% higher than the rest of the country--and that it is hoped that the REGARDS study will help to determine which factors are playing a part.



Other factors at play

So far, Howard and colleagues have recruited about half of the REGARDS participants--the aim is to have 30 000 in total, half of whom will be African American, half white. Half will be from the Southern states, and half will be from non-Southern states. All participants will be over 45, and half will be women. The study will run for five years and is being funded by the National Institutes for Neurological Disorders and Stroke (NINDS).

The analysis presented last week is based on the first 11 606 participants and, as mentioned, shows no difference so far between those living in the South and those not, except that those in the Stroke Belt are more likely to have their hypertension controlled. However, adjustment for demographic, socioeconomic, and risk-factor confounders largely mediated the regional difference in control, but had little impact on the other comparisons.

"The lack of regional differences in awareness, treatment, and control of hypertension implies that factors other than hypertension may be contributing to the excess stroke mortality in the Stroke Belt," Howard says.

Other possible factors include socioeconomic status, diet, quality of healthcare facilities, smoking, and infections. "We will look at these hypotheses and others over the course of the REGARDS study," he noted.



African Americans less likely to have hypertension under control

The study also looked at racial differences and showed that blacks are more aware of their hypertension than whites and more likely to be getting treatment for problem. They are, however, less likely to have their hypertension under control than whites.


Differences in awareness, treatment and control of hypertension between blacks and whites









Hypertension awareness, treatment, and control
Blacks (%)
Whites (%)
p
Awareness
92.8
89.2
<0.0001
Treatment
91.0
86.7
<0.0001
Control
61.7
70.1
<0.0001











To download tables as slides, click on slide logo below



"There are a number of possible reasons for this," says Howard. "First, we know that African Americans are going to the doctors and getting treatment, but there is no adequate follow-up; they are not returning." There could also be socioeconomic factors at play, he noted, so that blacks are getting prescriptions but cannot afford to fill them. Differences in the efficacy of drugs between the races may play a part, as may physician bias in terms of how aggressively they treat different groups of patients, he notes.

"Although we don't know the answer, the message is clear: interventions aimed at reducing the racial gap in hypertension rates need to focus on improving hypertension control," he concludes.



Stroke Belt is result of poor BP control in African Americans

February 14, 2005

New York, NY - Hypertension expert Dr Franz Messerli (St Luke's-Roosevelt Hospital, New York, NY) told heartwire he would like to take issue with the conclusions of the study. REGARDS illustrates that the so-called "Stroke Belt" is, to some extent, the result of poor blood-pressure control in African Americans, he believes.

"By recruiting a total of 30 000 patients, half of them African American and half white, half of whom live in the South and half in the North, the authors created an artificial study design. In reality, three times more African Americans are living in the South than in the North.

"Clearly, therefore, a study with a forced 50-50 racial distribution will not give us a realistic picture of the true prevalence of uncontrolled hypertension in the South, which is one of the main reasons for the existence of the so-called Stroke Belt. Mutatis mutandis, more aggressive blood-pressure control in African Americans is prone to have a much larger impact on stroke reduction in the South than in the North."

But Howard responded to heartwire that although Messerli is correct in pointing out that REGARDS results in a population nonrepresentative of the general US population, the sampling approach employed requires that "adjustment" be made for race when examining the geographic disparities and vice versa.

"It is important to note that these adjustments were made in the current report, and as such the interpretation of the results should be that the lack of a geographic difference in awareness and the trend for higher treatment and control in the Stroke Belt is made after adjustment for race. As such, the concerns of Dr Messerli are not applicable to this analysis."






















Source









  1. Howard G, Prineass 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. American Stroke Association International Stroke Conference 2005; February 2-4, 2005; New Orleans, LA.

Source...
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