Public Release: 

Study Finds Incidence Of Stroke Over 40 Percent Higher Than Previously Stated Figures

American Heart Association

Brian Henry or Trish Moreis
AHA News Media Relations
Omni Rosen Hotel
(407) 370-6151
NR 98-4855 (Stroke/Broderick)

ORLANDO, Feb. 6 -- The number of Americans afflicted with a stroke each year is estimated to be about 500,000 -- but that number is too low, according to a report in today's Stroke: A Journal of the American Heart Association. The study, based on a population more representative of the United States than the groups traditionally investigated to gauge stroke's impact on the nation, estimated that at least 731,000 first-ever and recurrent strokes occur each year -- 40 percent more than the 500,000 figure quoted by the government.

At the time this study was conducted, researchers compared their findings against the Framingham Heart Study statistics which stated that 500,000 people have a stroke each year. According to the American Heart Association, 600,000 people have a stroke each year. This figure comes from the National Center for Health Statistics and is based on the Atherosclerotic Risk in Communities study of the National, Heart, Lung and Blood Institute (NHLBI).

Previous studies have been based on the Rochester, Minn., and Framingham, Mass., populations, which are primarily white and whose socio-economic status is relatively high, says Joseph Broderick, M.D., professor of neurology, University of Cincinnati Medical Center, and first author of the Stroke journal paper, which is based on the Greater Cincinnati/Northern Kentucky population.

"Dr. Broderick, using modern sampling techniques to evaluate our changing and aging population, has shown the current magnitude of stroke is significantly higher than previously thought," says Michael D. Walker, M.D., Director of the Division of Stroke, Trauma and Neurodegenerative Diseases at the National Institute of Neurological Disorders and Stroke (NINDS). "With the advent of new and effective treatments for acute stroke, we can now project with greater accuracy those parts of the population who will benefit and plan accordingly."

Broderick says that this population was selected for the University of Cincinnati study, because it is more representative of the racial and economic diversity of the United States.

The Greater Cincinnati/Northern Kentucky Stroke study, funded by NINDS, counted the number of people who had suffered recurrent strokes -- information not fully represented in previous epidemiological studies, he says.

"We're not just interested in first-ever stroke," adds Broderick. "When someone has another stroke, it's a huge burden to the healthcare system. The burden of recurrent strokes is an understated problem. Even if our rates did not change at all, our numbers will increase as people live longer.

"These new numbers in our report emphasize that stroke needs more attention," says Broderick. More accurate estimates of the number of people who suffer stroke should provide a "wake-up call" to federal government officials about the severity of this disease, particularly in the African-American population, and the need for more research on stroke prevention and treatment, he adds.

The amount of money spent by the federal government on research about stroke already is low "when compared to any disease that's such a major killer and disabler," stresses Broderick. National Institutes of Health spent just over $120 million in Fiscal Year 1996 on research on stroke, which ranks as the No. 1 cause of disability in the United States and the nation's No. 3 cause of death.

Prior to the Cincinnati/Northern Kentucky study, it was already known that stroke severely affects the African-American population. Death rates for stroke are 97 percent higher for black males, when compared to white males, and 71 percent higher for black females than for white females, according to the American Heart Association's new Heart and Stroke Statistical Update.

In the new study, designed to be the first large, population-based investigation of trends in stroke incidence rates and outcome within a biracial population, Dr. Broderick and his colleagues found that during 1993 the incidence rate of stroke was 1.6 times greater for blacks than the overall age and sex-adjusted incidence rate of stroke among the white population of Rochester, Minn., during 1985-1989.

In the new study, the incidence rate was determined by counting the number of first-ever strokes and recurrent among people who were hospitalized for the condition and the number of strokes that were detected at autopsy.

The University of Cincinnati scientists also found that blacks in Greater Cincinnati under the age of 65 had a two to four times greater incidence of first-ever stroke compared with the rates among whites of similar age in the Rochester population. Age-specific stroke incidence rates were similar for elderly blacks and whites, however.

Application of the researchers' findings among blacks to the projected 1996 black population of the United States indicated that there were 138,100 strokes among blacks in the United States during 1996.

"These differences between blacks and whites with respect to stroke incidence rates mirrors the differences in stroke mortality rates between blacks and whites in the US population," the scientists write in the journal report.

The overall incidence rate for all first-ever strokes in people who were hospitalized or whose stroke was determined at autopsy among blacks in the Greater Cincinnati region was 288 per 100,000. This does not include transient ischemic attacks (TIAs), often regarded as precursors to strokes. The overall incidence rate for first-ever and recurrent stroke was 411 per 100,000. By comparison, the overall incidence rate of first-ever stroke among whites in Rochester, Minn. during the period 1985-1989 was 179 per 100,000.

Though the recurrence rate of stroke among whites in the Rochester population is not known, the researchers estimated that the ratio of first-ever to recurrent stroke for whites in Rochester is similar to that for blacks in Greater Cincinnati, meaning the expected incidence rate of total stroke for whites in Rochester would be 256 per 100,000 population.

Applying that rate of total stroke in Greater Cincinnati/Northern Kentucky to the remainder of the 1996 United States population would indicate that there were 593,000 strokes among whites and nonblack segments of the population during 1996, thus adding the that figure to the 138,100 strokes among blacks equals the researchers' figure.

"Even our numbers could underestimate the number of strokes for the United States," says Broderick. "We're assuming that the stroke rates among whites in Rochester is the same everywhere and the same for other ethnic populations, some of which probably have higher stroke rates."

Co-authors include Thomas Brott, M.D.; Rashmi Kothari, M.D.; Rosie Miller, R.N.; Jane Khoury, M.S.; Arthur Pancioli, M.D.; James Gebel, M.D.; Debbie Mills, M.D.; Laura Minneci, B.A. and Rakesh Shukla, Ph.D.


Media advisory: Dr. Broderick can be reached at (513) 558-3760. (Please do not publish telephone numbers.)


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