The study's lead author says the findings suggest that stroke risks are shaped early in life, and that a stroke is a "lifelong" disease.

"In other words, to succeed in preventing stroke, we need to examine how the roots of stroke risk are established in childhood," said J. Robin Moon, a researcher at the Harvard School of Public Health in Boston, Mass, in an email.

Moon and her colleagues, who published their findings in the journal Stroke, looked at a national database of Americans over 50 years old, and compared information on more than 14,000 non-Hispanic whites and about 1,500 Hispanics who had not experienced a stroke before 1998.

The researchers followed those people over the next 10 years.

They found that at age 60, about five out of 1,000 non-Hispanic white men had suffered a stroke. That number increased to eight in 1,000 for U.S.-born Hispanic men, or those who had immigrated to the U.S. before age seven. But the figure for foreign-born Hispanic men was just four out of 1,000.

Among women at 60 years old, the numbers were nearly identical. Five out of 1,000 white women had suffered a stroke. The number was seven out of 1,000 for U.S.-born Hispanic women and four out of 1,000 for foreign-born Hispanic women.

When the researchers adjusted for socioeconomic factors, the risk difference between U.S.-born Hispanics and non-Hispanic whites disappeared.

But even after adjustment for various factors, foreign-born Hispanics had 42 percent lower stroke risk than non-Hispanic whites with similar socioeconomic backgrounds.

Though the researchers do not know exactly why the difference is so stark, there are a few popular theories.

One is that the healthiest citizens of one country will immigrate to another. A second theory is that immigrants may return to their birth country to spend their old age and eventually die, which would influence death rates.

However, the researchers said another explanation could be that there may be factors that lead U.S.-born Hispanics to have an increased risk for disease, including segregation and poverty.

The study did have some limitations, including the fact that strokes were self-reported by the participants or their families, and the definition of a stroke can mean different things to different people.

Dr. Mitchell Elkind, an associate professor of neurology and epidemiology at Columbia University in New York, said it would have also been nice to see information on which countries the foreign-born Hispanics came from, but he said this type of research is important.

"If we could figure out why people from other cultures -- in particular among Hispanic cultures -- are at a lower risk, there might be a way to replicate their activities here in the U.S.," said Elkind, who was not involved in the new research.

However, the new study's authors have observed a similar pattern of divergence among non-Hispanic Americans, all born in the U.S.

Maria Glymour, one of the new study's authors, has analyzed data focused on the southeastern U.S., also known as the "stroke belt" -- where the stroke death rate is about 50 percent higher than in the rest of the country.

"One thing that is interesting in the region is that people born in the stroke belt tend to maintain their increased risk if they move away," said Glymour, an assistant professor at the Harvard School of Public Health.

But while a person cannot change where they were born, Elkind said there are some things they can do to reduce their risk of a stroke.

He said people should see their physician regularly, make sure their blood pressure is not elevated and watch their diet for -- among other things -- too much salt and red meat.

According to the American Stroke Association, about 795,000 people in the U.S. suffer a new or recurrent stroke each year, and more than 137,000 die from one.

SOURCE: bit.ly/xYLDsp Stroke, online February 21, 2012.

• A Permanent Economic Emergency