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A new study from the University of Michigan Stroke Program (Ann Arbor) indicates that a type of stroke that kills one-third of its victims appears to be more common in women and Mexican-Americans than in non-Hispanic white men.

In a paper published online by the journal Neurology, the U-M researchers reported that women had a 74% greater chance of suffering a type of stroke related to a ruptured brain aneurysm. Mexican-Americans of both genders had a 67% greater chance.

The type of stroke measured in the study is called a subarachnoid hemorrhage, or SAH. The new research may help public health officials reach out to higher-risk groups with information on prevention and the importance of rapid treatment.

"Physicians and public health officials should help Mexican-Americans and women take steps that might prevent subarachnoid hemorrhage, and other types of stroke that have already been shown to be more common in these two groups," says senior author Lewis Morgenstern, MD.

He added, "Given that Mexican-Americans are the largest and fastest-growing minority group in the U.S., it's important to understand how this condition might affect them differently, and tailor messages to them."

The new paper also gives a "real world" picture of the risk of dying from an SAH, which was nearly one in three in the geographic region in the study. That region, Nueces County, Texas, containing the city of Corpus Christi, has a large Mexican-American population and does not have a major university health system.

While African-Americans and Asian-Americans were included in the initial screening portion of the study, which reviewed the medical records of 6,550 stroke patients, the researchers said their numbers were too small to assess any differences in risk of SAH.

Morgenstern, director of the stroke program at the University of Michigan Cardiovascular Center, is a professor of neurology and neurosurgery at the U-M Medical School, and of epidemiology at the U-M School of Public Health. The first author on the study, Sonia Eden, MD, is a former chief resident in neurosurgery at U-M.

The study is the latest to arise from the Brain Attack Surveillance in Corpus Christi (BASIC) project. The project involves surveillance for all strokes and mini-strokes in Nueces County, and detailed analysis of anonymous patient records.

Using data from BASIC, Morgenstern and his colleagues previously have shown differences between ethnic groups and genders in other types of stroke including the most common type, ischemic.

The latest paper is based on data from 107 subarachoid hemorrhage patients over age 44 who experienced strokes between 2000 and 2006. The researchers said it was unclear why the ethnic and gender differences were seen in the new study, because they were able to account and adjust for blood pressure, age, excessive alcohol use, smoking and health insurance status.

In all, 60% of the SAH cases occurred in Mexican-Americans, who make up just 48% of the population over age 45 in the study area; 40% were in non-Hispanic whites, who make up 52% of the over-45 population in the area.

And 67.3% of SAH patients were women, significantly higher than the 53.5% of the population in the area that is female. The researchers said Mexican-American women had the highest risk.

SAHs account for 3% of the 780,000 strokes that occur in the U.S. each year. Because these strokes arise from ruptured aneurysms, which arise for unknown reasons at any stage, subarachnoid hemorrhages can occur at any time of life.

The signs of an SAH usually include a sudden, extremely severe headache, often compared to a "thunderclap" inside the head. Patients also may experience neck pain, nausea and vomiting, or may lose consciousness. Morgenstern said that, although SAH carries daunting odds, it can be treated if a patient reaches a hospital where a neurosurgeon or interventional radiologist can close off the ruptured aneurysm and stop the bleeding.

The BASIC study, including the analysis performed for the latest study, is funded by the National Institute of Neurological Disorders and Stroke, part of the National Institutes of Health.