As many as 18% of adults who have no history of stroke report having had at least one symptom of stroke, according to results of a large national study published in the October 9 Archives of Internal Medicine.

Previous studies using brain imaging to screen individuals without a history of stroke found that 11% of those ages 55 to 64, 22% of those ages 65 to 69, and 43% of those older than 85 show evidence of stroke despite never having been diagnosed with the condition. Because awareness of stroke symptoms is low, it is possible that these people had symptoms but did not recognize them or that the symptoms did not reach the threshold necessary for a stroke diagnosis, the investigators suggested.

Virginia J. Howard, MSPH, of the Department of Epidemiology at the University of Alabama at Birmingham, and colleagues analyzed data from the REGARDS (REasons for Geographic And Racial Differences in Stroke) study, a random sample of 18,462 adults older than 45 (average age, 65.8) who had not been diagnosed with stroke. To ensure analysis of many individuals at risk for stroke, the researchers included 7,567 African-Americans (41% of the total sample—a higher ratio than in the general population), and 6,534 (35.4% of the sample) were residents of the "stroke belt." In telephone interviews, participants provided information about demographics, general quality of life, and medical history, including whether a physician had ever told them they had had a stroke and whether they had experienced the sudden onset of any of six stroke symptoms. Brief physical examinations, including blood pressure measurements, blood samples, and electrocardiography, were conducted three to four weeks later. A stroke risk score was calculated for each participant, based on demographics, behaviors, and other risk factors, with higher scores indicating a greater risk for stroke.

African-Americans and those with lower incomes, less education, poorer health status, and higher Framingham Stroke Risk scores were more likely to have had stroke symptoms. "The last finding suggests that at least some of these symptoms may represent stroke events that did not reach the threshold required for clinical diagnosis," Ms. Howard and colleagues said. "These undiagnosed or unrecognized events could have a substantial impact on cognitive functioning or personality and could also be powerful harbingers of subsequent major strokes."

It is not known whether individuals found to have a high risk for stroke visited a physician for their symptoms, but previous studies have shown that many people do not seek medical care for stroke symptoms, and if they do, they do not seek it immediately. "Targeted education on the warning signs of stroke and risk factor reduction efforts for individuals who report stroke symptoms may be helpful in improving early recognition and in the prevention of stroke," the authors concluded.

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