NEW YORK (Reuters Health) - Brothers and sisters of people who have had a stroke are nearly twice as likely as the average American to experience a stroke themselves, according to observational data reported at the American Academy of Neurology's annual meeting in Boston on Wednesday.
"The risk to the sibling is especially prominent in Mexican-American men with over a doubling of the risk compared to the general population," Dr. Lewis B. Morgenstern from University of Michigan, Ann Arbor, told a gathering of reporters at the conference. Sibling risk is also particularly high in non-Hispanic white women.
The study involved 807 adult brothers and sisters of 181 patients who had a stroke or mini-stroke, known as a TIA, in Nueces County, Texas. Fifty-nine percent of the stroke patients were Mexican American; the rest were non-Hispanic whites.
Overall, the risk of stroke for siblings of stroke cases was 92 percent greater than would be expected based on national prevalence estimates. The risk varied by gender of the sibling and their ethnicity.
"Sisters and brothers of non-Hispanic white women who had a stroke had a significant 2.7-fold increased risk of stroke compared to the general population. But siblings of non-Hispanic white men did not have an increased risk of stroke," Morgenstern reported.
Among Mexican Americans as a group, the stroke risk ratio was 2-fold higher than expected. This was due to a 2.6-fold higher risk in siblings of Mexican-American men. The risk for siblings of Mexican-American women was 1.47-fold higher, which was not significant from a statistical standpoint.
Summing up, Morgenstern said: "We've already shown in other research that Mexican Americans have a higher risk of stroke compared to non-Hispanic whites -- and on top of that we are now able to show that their siblings have more risk of stroke."
He also pointed out that Mexican Americans have more siblings than non-Hispanic whites. The average number of siblings in this study was five among Mexican Americans versus two among non-Hispanic whites. They are also more likely to live in the same geographic area compared with non-Hispanic whites.
Therefore, it's likely, he added, that environment and/or genetics play a role in the observed association.
