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MEXICAN‐AMERICANS HAVE HIGHER STROKE RATES, BUT LOWER MORTALITY RATES

Laino, Charlene

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SAN DIEGO—A new study presented here at the American Neurological Association Annual Meeting points to new evidence of ethnic gaps in stroke outcomes.

The study, led by Lewis B. Morgenstern, MD, reported that Mexican-Americans are more than twice as likely to have a stroke as age-matched whites. In addition, Mexican-Americans are less likely to die in the 36 months after a stroke than their white counterparts.

Dr. Morgenstern, Director of the University of Michigan Stroke Program in Ann Arbor, called the results of his study a “wake-up call” about the third-leading cause of death in the nation. Mexican-Americans make up two-thirds of Hispanics, the nation's largest minority group.

The increased stroke burden holds true for both ischemic stroke and intracerebral hemorrhage and for adults of all ages, he said. The greatest disparity was observed in Mexican-Americans, 45- to 59-years-old – who were 2.04 times more likely to suffer a stroke compared with non-Hispanic whites in that age group.

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THE ‘HISPANIC PARADOX’

And, in what has been identified as the “Hispanic paradox,” Mexican-Americans were 42 percent less likely to die in the first 28 days after a stroke than non-Hispanic whites. Overall, 7.2 percent of Mexican-Americans died by 28 days compared with 13.3 percent of non-Hispanic whites.

By 36 months, mortality was still 21 percent lower in Mexican-Americans, the study showed. At 36 months, 29.5 percent of Mexican-Americans had died, compared with 44.2 percent of non-Hispanic whites.

“Despite lower socioeconomic status, poor access to care, and more diabetes, Mexican-Americans have a lower case-fatality and 36-month all-cause mortality than non-Hispanic whites,” Dr. Morgenstern reported. “Further research is needed to determine the factors related to increased incidence and decreased mortality in Mexican-Americans.”

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POPULATION-BASED STUDY

The findings came from an ongoing NIH-funded study called “BASIC,” the Brain Attack Surveillance in Corpus Christi, a population-based program to determine how common stroke is in the Hispanic community, and to delineate the factors that influence the rates of stroke and mortality due to stroke. The study is being conducted in Nueces County, TX, an urban county with 313,645 residents in which 56 percent of residents are Mexican-American and 95 percent reside in Corpus Christi.

Dr. Morgenstern said Nueces County provides “a best case scenario” because of its small immigrant population. “Most of these Mexican-American families have been in the US for several generations and have few cultural and language barriers to getting medical care,” he said. “I would think the disparity would be even worse in cities like San Diego or Miami, where the immigrant populations are larger.”

Bernadette M. Boden-Albala, DrPH, Director of Research and Project Manager for the Northern Manhattan Stroke Study at the Neurologic Institute at Columbia University in New York City, said that “the study provides one of the first examples of the ‘Hispanic Paradox’ in ischemic stoke.”

Physicians have been puzzled for years by reports of the Hispanic Paradox in other diseases, she told Neurology Today. “It's best known in infant mortality,” she said. Also, studies have shown that Mexican-Americans, who have high rates of obesity and diabetes, are less likely than whites to die of heart disease.

“Despite the fact they should have higher mortality due to lower socioeconomic status and less access to health care, for some unknown reason, they do better,” she said.

The higher rates of stroke incidence mirror those found in the Northern Manhattan Stroke Study, another population-based incidence study, added Dr. Boden-Albala, one of its investigators. In that study, blacks had a 2.4-fold and Hispanics a two-fold increase in stroke incidence, compared with whites (Am J Epidemiol 1998;147:259-268).

Figure. Dr. Lewis B....
Figure. Dr. Lewis B....
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WHY THE PARADOX?

Dr. Boden-Albala speculated that social support systems – for example, greater involvement of extended family in caring for relatives who are sick – may help explain lower mortality rates among Mexican-Americans. “Hispanics have tight social support, much stronger than African-Americans or whites and this social support may help these patients after a stroke,” she said.

But the fact that these people have been in the country for several generations would tend not to support that theory, she said. “Further work is clearly needed.”

Dr. Morgenstern, too, was at a loss to completely explain the paradox why Mexican-Americans have higher incidence of stroke but better survival rates, pending further study.

Hispanics are known to have a high rate of diabetes, which has prompted many stroke specialists to speculate that Hispanics might have a higher risk of ischemic stroke in smaller vessels, which could be attributed to damage caused by hyperglycemia, he said.

But when Dr. Morgenstern and colleagues performed an in-depth analysis of 402 validated ischemic strokes in the BASIC study, there was no statistically significant difference between Mexican-Americans and non-Hispanic whites in any ischemic stroke-subtype.

“Other factors contribute to the stroke risk faced by Mexican-Americans that still need to be determined,” he said. For instance, a genetic predisposition to vascular malformations that tend to cluster in Mexican-American families might play a role. But Dr. Morgenstern cautioned that far more studies would be needed to determine what is behind the differences in stroke risk and death rates.

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STROKE PREVENTION: FACTORS INFLUENCING BEHAVIOR

The investigators are already examining factors that might affect Mexican-Americans' behavior regarding stroke prevention, access to preventive care, and seeking treatment for acute stroke. Another new study within BASIC will explore the roles that spirituality, religiosity, fatalism, and depression may play. Also, BASIC researchers are studying the effectiveness of different approaches to raising stroke awareness, including a program that teaches hundreds of middle school students about stroke risks and the importance of a rapid response.

In the meantime, Dr. Morgenstern said he hopes the findings, however paradoxical, prompt more than just the translation of stroke-education materials into Spanish. For example, patients who are at risk of stroke need to be informed of the symptoms that necessitate a call to 911 as well as how effective prompt therapy can be, he said.

Figure. Dr. Bernadet...
Figure. Dr. Bernadet...
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Dr. Morgenstern also called on physicians to spend more time with patients, listening to their concerns. Specific issues that should be addressed in terms of barriers to seeking acute and preventive stroke care include fear of the health care system and a lack of understanding of how care is provided in the US, he added.

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ARTICLE IN BRIEF

✓ A new analysis of data from a population-based study in Corpus Christi, TX, showed that Mexican-Americans, 45- to 59-years-old – were 2.04 times more likely to suffer a stroke compared with non-Hispanic whites in that age group. But Mexican-Americans were 42 percent less likely to die in the first 28 days after a stroke than non-Hispanic whites.

©2005 American Academy of Neurology

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