Stroke: Mexican-Americans have higher rates of stroke recurrence

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Compared with non-Hispanic whites, Mexican-Americans have a higher rate of stroke recurrence, by almost double, but all-cause mortality rates between the ethnic groups did not differ, according to a study published in the September issue of Stroke.

Atrial fibrillation (AF) heightens a patient’s risk for stroke, and while the use of warfarin (Coumadin, Bristol-Myers Squibb) has been shown to reduce the risk of stroke by 64 percent, prior research has found that warfarin's effectiveness may be suboptimal in Hispanics and other racial and ethnic groups.

To study this notion further, Jennifer R. Simpson, MD, of the University of Michigan Medical School and University of Michigan School of Public Health in Ann Arbor, Mich., and colleagues looked at data of 236 patients—88 Mexican Americans and 148 non-Hispanic whites—to understand the ethnic differences of stroke recurrence and post-stroke mortality in AF patients with stroke.

The researchers used methods and populations from the previous Brain Attack Surveillance in Corpus Christi Project (BASIC) study to enroll patients with ischemic stroke or transient ischemic attack (TIA) between January 1, 2000, and June 30, 2008.

According to the researchers, Mexican-Americans were younger, less likely to have completed all 12 years of education, have diabetes and less likely used a primary care physician compared to non-Hispanic whites.

At discharge, 37 percent of Mexican-Americans were taking warfarin compared to 40 percent of non-Hispanic whites at baseline stroke/TIA. In contrast, 16 percent of Mexican-Americans and 19 percent of non-Hispanic whites were discharged without antiplatelet or anticoagulant drugs.

After a mean follow-up of 427.5 days, 19 Mexican-Americans and 14 non-Hispanic whites experienced a recurrent event—all but one was an ischemic stroke event. The authors found that there was no ethnic differences at the time of stroke recurrence in the groups of patients administered warfarin, 38 percent for Mexican-Americans and 36 percent for non-Hispanic whites.

These rates for patients not administered antiplatelet and anticoagulant medications were 7 percent and 19 percent, respectively.

When the National Institutes of Health Stroke Scale (NIHSS) was used, researchers found that first recurrent events were significantly higher in Mexican Americans than in non-Hispanic whites, scores were recorded to be 10 and four, respectively.

Three Mexican-Americans and one non-Hispanic white had a second recurrent stroke that took place during the study period and one Mexican-American experienced three recurrent strokes.

Simpson and colleagues found that survival free rates of stroke were 0.99 and 0.85 at 28 days and one year for Mexican-Americans compared to 0.98 and 0.96 for non-Hispanic whites; however, Mexican-Americans experienced a higher risk for stroke recurrence.

After a mean follow-up of 523.5 days, 139 patients—52 Mexican-Americans and 87 non-Hispanic whites—died. However, the researchers said that ethnicity did not affect survival.

“This population-based study of stroke/TIA patients with AF found that Mexican-Americans have more than double the risk of recurrent stroke and a greater severity of recurrent stroke than do non-Hispanic whites,” the authors wrote. “A higher risk of recurrence in Mexican-Americans could be explained by ethnic differences in warfarin use or monitoring, although we found no ethnic differences in the proportion of cases on time of stroke recurrence.”

While the authors noted that access to care and socioeconomic factors may have contributed to the higher risk of recurrent stroke in Mexican-Americans, the researchers said that this higher risk of recurrent stroke in this population could have been formed by noncardioembolic recurrent strokes.

The authors called the fact that they did not find differences in post-stroke mortality among ethnicities “surprising,” as recurrent stroke was a “potent predictor of mortality and that Mexican-American’s had more recurrent strokes that were more severe than non-Hispanic whites.

“Aggressive stroke prevention measures are warranted in this population, and further study is needed to investigate reason for the higher risk of recurrence and severity in Mexican-Americans,” the authors concluded.