SAN ANTONIO -- A large nationwide study that includes neurologists from Mayo Clinic has found that blacks are substantially less likely than whites to know that they have atrial fibrillation or to use warfarin, the most common treatment for the condition. Atrial fibrillation, an abnormal heart rhythm, significantly increases risk of stroke. Warfarin is known to reduce that risk.
Researchers say the findings could help explain why the black population in the U.S. has a higher incidence of both stroke and death from strokes, compared to the white population. They presented their findings at the American Heart Association's 2010 International Stroke Conference in San Antonio. The study will also be simultaneously published in Stroke: Journal of the American Heart Association.
"The reasons for the racial discrepancy are not known," says James Meschia, M.D., Mayo Clinic neurologist and director of the Comprehensive Stroke Center at Mayo's campus in Florida. "But they are consistent with other studies that show blacks are less likely to receive the care they need to treat stroke risk factors such as diabetes and hypertension."
"These findings should lend urgency to focused efforts to improve patient education and medical treatment across the board," says Dr. Meschia, who who is presenting the findings on behalf of investigators participating in the study, known as REGARDS (The Reasons for Geographic and Racial Differences in Stroke).
From 2003 to 2007, REGARDS enrolled 30,239 men and it deliberately "oversampled" blacks (42 percent) as well as residents of the Southeastern "Stroke Belt." Fifty-six percent were from North Carolina, South Carolina, Georgia, Alabama, Mississippi, Tennessee, Arkansas, and Louisiana, and 44 percent were from other areas of the country. All residents of Stroke Belt states are known to have high stroke death rates, but blacks are at even greater risk, Both blacks and residents of these states are known to have high stroke death rates according to the National Institutes of Health.
For this study, atrial fibrillation was diagnosed using an electrocardiogram (ECG) test given to participants in their homes. Before the visit, participants were asked by telephone if a physician or a health professional had ever told them that they had atrial fibrillation, and they were also asked what medications they were using.
Of those participants whose ECG showed atrial fibrillation, 88 (20 percent) were black, and 344 were white. While 60 percent of the total group (black and white) were aware of their diagnosis, the odds that blacks knew they had the condition were less than one-third of those reported for whites, researchers say.
They further found that the odds of blacks being treated with warfarin, which reduces stroke risk by 60 percent, were one-fourth those of whites.
In other words, blacks in this study with atrial fibrillation were two-thirds less likely to know they had the disorder and three-fourths less likely to be treated with warfarin, the standard of care.
Reasons for the racial disparity are not known from this study, but researchers suggest several explanations. Many study participants might have been undiagnosed because atrial fibrillation is often not symptomatic, Dr. Meschia says. Or, participants may have been diagnosed but did not remember or fully appreciate the significance of the condition, he says. Dr. Meschia says other possible reasons could include utilization or delivery of health care, reluctance by physicians to use warfarin in patients with multiple health conditions, or disinclination by patients to use the drug.
Insurance status was not a factor, the researchers add, because the majority of study participants were over age 65 and were covered by Medicare.
"Whatever the reasons behind these observations, it appears that there is a missed opportunity to prevent stroke and other thromboembolic complications from atrial fibrillation because many individuals may fail to have the condition diagnosed and/or fail to receive treatment with warfarin," Dr. Meschia says. "It would benefit public health if future research could tease out the reasons behind this disparity."
The study was funded by a grant from the National Institute for Neurological Disorders and Stroke, a branch of the National Institutes of Health.
For more information about atrial fibrillation and stroke, or to request an appointment, visit www.mayoclinic.org.
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