TUESDAY, Sept. 23 (HealthDay News) -- American Indians have a higher incidence of stroke than blacks or whites, and their first strokes may be more deadly, a new study suggests.

The study included 4,507 members of 13 American Indian tribes in Arizona, Oklahoma and North and South Dakota. It found that American Indians have a stroke rate of 679 per 100,000, compared to 607 per 100,000 for blacks and 306 per 100,000 for whites.

None of the participants, ages 45 to 74, had a history of stroke when they were recruited for the study from 1989 to 1992. Almost 60 percent of the volunteers were women.

During more than 13 years of follow-up, 306 participants suffered a first stroke, and most of them were in their mid-60s when it occurred. Ischemic stroke -- caused by a blockage that cuts off blood supply to the brain -- accounted for 86 percent of the cases, while 14 percent were caused by hemorrhagic (bleeding) stroke.

The death rate was 18 percent within one month of stroke and 32 percent within one year of stroke, according to the study, which was published in the Sept. 23 issue of the journal Circulation.

High rates of cigarette smoking, hypertension, and diabetes among American Indians may explain why they have a higher stroke incidence than blacks or whites, suggested study lead author Dr. Ying Zhang, an assistant professor at the College of Public Health at the University of Oklahoma Sciences Center, and colleagues. Interventions that target these risk factors may help reduce stroke risk.

The researchers also identified a strong link between stroke and protein in the urine, which is a marker for kidney dysfunction often associated with diabetes. Further studies into the association between kidney function and stroke are needed, the study authors concluded.

They found no association between alcohol use and stroke incidence among American Indians.

More information

The U.S. National Institute of Neurological Disorders and Stroke has more about stroke.