Mexican Americans with Atrial Fibrillation Have Twice the Risk of Recurrent Strokes as Non-Hispanic Whites
By Peggy Noonan and Mellanie True Hills
New research has revealed important ethnic differences in the risk of stroke in people with atrial fibrillation.
Mexican Americans with atrial fibrillation who have had a stroke are more than twice as likely to have another stroke than comparable non-Hispanic whites, according to a new study published in the latest issue of the American Heart Association journal Stroke. The recurrent strokes were more severe in the Mexican Americans, but there was no difference between the two groups’ stroke deaths.
These findings were derived from data collected by the Brain Attack Surveillance in Corpus Christi Project, a population-based study that tracked ischemic strokes and transient ischemic attacks (TIAs, or “mini-strokes”) between January 2000 and June 2008 in people with atrial fibrillation. Participants were age 45 or older and lived in Nueces County (Corpus Christi) on the Gulf coast of Texas.
The new study compared 88 Mexican American and 148 non-Hispanic white stroke survivors with atrial fibrillation. The researchers were not surprised to find higher risk of stroke recurrence in Mexican Americans, but another finding was unexpected. “The greater severity of recurrent strokes in Mexican Americans was surprising,” said study coauthor Darin B. Zahuranec, MD, of the University of Michigan Cardiovascular Center in Ann Arbor.
The study found that Mexican American stroke survivors with afib had 19 recurrent strokes in the follow up period, which averaged about 14 months, compared to 14 strokes in whites. Interestingly, all but one of those strokes was ischemic, the type caused by a blockage such as a clot. The study also found the following differences between the Mexican Americans and whites:
- Age: Mexican Americans were younger, with an average age of 78 compared to whites’ average age of 82
- Diabetes: Mexican Americans were more likely to have diabetes, at 44 (50%) compared to 39 (26%) for whites.
- Primary Care Physician: Mexican Americans were less likely to have a primary care doctor, with 79 (90%) having a primary care doctor compared to 143 (97%) for whites, despite there being “no ethnic difference in health insurance coverage in this community.”
- Education: Mexican Americans were less likely to have finished high school, with 20 (23%) of the Mexican Americans having completed 12 years of education compared to 111 (77%) of the whites.
The difference in diabetes is interesting, but the researchers noted that “the change in the ethnic association with risk of recurrence was more due to education than to diabetes.” They also noted that “lower educational levels might directly contribute to difficulty in following directions for warfarin monitoring” and dietary restrictions, “or it could be a marker for lower socioeconomic status.”
Stroke Prevention Medication
Both groups were given anticoagulant or antiplatelet medications when released from the hospital after their initial strokes. But only 40% or less in both groups actually used warfarin, either at the time of release or at the time of their recurrent stroke.
Since the study didn’t provide data on outpatient use of warfarin, the researchers couldn’t evaluate whether clotting risk was adequately controlled. That’s important because less effective anticoagulation control might explain why Mexican Americans had more severe strokes than whites.
Lack of data also prevented the researchers from assessing stroke risk using tools like CHADS2 scores.
Despite these differences, survival rates after stroke were about the same in both ethnic groups. That’s surprising, considering the higher risk of recurrent strokes, and more severe strokes, in Hispanics. The researchers note that having a better-than-expected mortality (death) rate in other diseases has been called the “Hispanic paradox.” However in this study, the Hispanic death rate isn’t lower, but is on par with mortality in whites, even though the disease is worse in Hispanics. Why? This may “be reflective of a broader protective effect of Hispanic ethnicity against mortality.”
It is important to note that the Mexican Americans in this study were less likely to have a primary care physician. Therefore, it’s reasonable to presume that they might not have been measuring and monitoring their INR sufficiently to gain the protective effects of warfarin. And without a primary care physician, it is likely that they did not receive information about food and drug interactions with warfarin and how to keep it under control.
There are new warfarin alternatives that will likely be approved very soon, but those without primary care physicians may not know about these new drugs that offer a viable alternative and don’t require the extensive monitoring that warfarin requires.
Cost may be an issue, too, because if they don’t have a primary care physician, they may also not be able to afford these newer medications. But there are programs that can help, and my hope is that we can find options to decrease these afib strokes in Mexican Americans, and in all who are at risk.
To learn more:
- American Heart Association Rapid Access Journal Report: Mexican-Americans with heart rhythm disorder have increased risk for second stroke, September 9, 2010
Peggy Noonan specializes in writing about health for consumers and medical professionals. She writes for leading national magazines and consumer publications as well as StopAfib.org.
Mellanie True Hills is founder and CEO of StopAfib.org and an atrial fibrillation survivor.