From January 2000 through December 2004, in a study of 1,345 stroke patients (median age 72), 53% of those with a first stroke were Mexican-Americans, said Lynda Lisabeth, Ph.D., of the University of Michigan School of Public Health, and colleagues.
Of these first-stroke patients, 126 had a recurrent stroke, and 417 died of any cause. The cumulative risk for recurrence at 30 days was 2.6%, rising to 7.5%, at one year, Dr. Lisabeth and colleagues reported in the September issue of the Annals of Neurology.
These findings came from the Brain Attack Surveillance in Corpus Christi (BASIC) project, a stroke study in Nueces County, a geographically isolated bi-ethnic community in southeast Texas.
Recurrent stroke differed significantly by ethnicity. The risk ratio for stroke recurrence for Mexican-Americans was 1.57 (95% confidence interval, 1.05-2.34) adjusted for demographics, stroke risk factors, and stroke severity, said the authors.
Those who had a recurrent stroke had a two- to three-fold increased risk of death due to any cause. Stroke recurrence and mortality were related to a similar extent across all ethnic groups. For non-Hispanic white patients, the risk ratio was 3.32 (CI 2.07-5.32), while the risk for Mexican Americans was 2.35 (CI, 1.42-3.88), the researchers reported.
"The magnitude of this association was considerably larger than other predictors of death in this population, including diabetes and coronary artery disease, and indicates that in both ethnic groups, secondary stroke prevention is critical to improve survival following ischemic stroke," the authors wrote.
Mexican-Americans with recurrent stroke were significantly younger than the non-Hispanic whites, and were more likely to have diabetes, whereas the non-Hispanic white patients were more likely to have atrial fibrillation and to smoke.
Interestingly, Dr. Lisabeth said, in the current model predicting all-cause mortality, survival after an ischemic stroke was better for the Mexican-Americans despite their increased risk of recurrence and the fact that recurrent stroke carried the same risk of dying in the two groups.
The researchers suggested that unidentified factors might contribute to their better survival, such as better social support and/or genetic factors. "Nonetheless," they said, "efforts to reduce stroke recurrence in this population are needed."
In reviewing the study's limitations, the researchers noted that the analysis of stroke recurrence is not straightforward because an early death would prevent recurrent stroke. Also, they noted that survival estimates from this stratified analysis were somewhat imprecise because of the small sample size within the strata. The relationship between ethnicity and recurrence may have resulted from residual confounding factors unaccounted for in the multivariable model.
Use of or compliance with secondary stroke prevention medications may influence risk for recurrent stroke. In this study, however, the investigators found that there were no ethnic differences in the number that reported taking medication.
Nonetheless, it is unclear, they said, whether differences between the two groups may exist in the control of traditional vascular risk factors, such as diabetes and hypertension. Differences in physician treatment, patient compliance, or differential drug effectiveness by ethnicity could also translate into increased stroke recurrence for the Mexican-Americans, they said. In the multivariate models in this study, it was not possible to explore these variables, due to the limited number of outcome events.
In this analysis, the researchers said, it would be useful to investigate the rate of other vascular events following stroke in future studies. Meanwhile, they advised caution in generalizing these findings to other communities, which might differ considerably in ethnic composition and sociodemographic structure.
- Reviewed by Zalman S. Agus, MD Emeritus Professor at the University of Pennsylvania School of Medicine
Annals of NeurologySource Reference: Lisabeth, LD, et al "Ethnic Differences in Stroke Recurrence" Annals of Neurology 2006;60: DOI:10.1002/ana.20943.