NEW ORLEANS—Among persons who have never had a stroke, merely having a high risk of stroke is associated with more rapid cognitive decline than having few or no stroke risk factors. Results from an observational study suggest that the decline in cognitive function is twice as rapid in those at high risk of stroke based on their Framingham Stroke Risk Function (FSRF) score, compared with persons considered to have an average risk, said George Howard, DrPh, at the 2008 International Stroke Conference.
The findings from Dr. Howard and colleagues are based on an analysis of the Reasons for Geographic and Racial Differences in Stroke (REGARDS) study, which included 30,201 community-dwelling black and white participants randomly selected from the 48 contiguous states.
“There’s growing evidence that cerebrovascular risk factors are associated with cognitive decline and also a growing appreciation that cognitive dysfunction may be a marker for subclinical cerebrovascular disease,” said Dr. Howard, Professor and Chair of Biostatistics at the University of Alabama in Birmingham.
Designing REGARDS
REGARDS included even numbers of blacks and whites and males and females; half were from the southern United States (also known as the “Stroke Belt”). Participants were recruited through the mail and via the telephone and were followed up with a 45-minute computer-assisted telephone interview that assessed their cardiovascular risk profile.
More than 27,000 participants were initially evaluated, of whom 2,833 were excluded because they had a history of stroke or transient ischemic attack. A six-item cognitive test, derived from the Mini-Mental State Examination, was administered yearly via telephone to 18,642 participants. Of these, 17,626 (mean age, 65.9) had two or more cognitive assessments and formed the basis for this analysis.
The researchers examined the association between the annual rate of decline of mean cognitive score and FSRF scores. Cognitive assessments were performed until the last follow-up or until participants had a stroke.
Stroke Risk Associated With Cognitive Decline
The FSRF, which produces a score from 0 to 100, was used to assess systolic blood pressure, medication use, diabetes, cigarette smoking, coronary heart disease, atrial fibrillation, and left ventricular hypertrophy. The mean FSRF score among participants was about 10, indicating a 10-year risk of stroke of 10%.
In participants with no risk of stroke during the following 10 years (FSRF score, 0), the annual rate of decline in the cognitive score was 0.02 points. Participants with an FSRF score that indicated an average risk of stroke (10.5% risk) had an annual rate of decline approaching 0.06 points. Those with a 31.5% risk (2 SD greater than average risk) had an annual rate of decline in excess of 0.11 points.
“Someone with an FSRF score of 30 lost cognitive ability more than twice as fast as someone with an FSRF score of 10,” said Dr. Howard. The three FSRF components that were indicative of cognitive decline were systolic blood pressure, diabetes, and left ventricular hypertrophy.
A 31–mm Hg increase in systolic blood pressure was associated with a 29% increase in the rate of cognitive decline. “It’s the blood pressure that makes the difference, not taking the [antihypertensive] medication,” stressed Dr. Howard. “It suggests that if you’re hypertensive and controlled, then it’s not strongly associated with cognitive decline, but if your blood pressure levels are high, then it’s associated with the decline. To prove this, though, would take a clinical trial.”
Diabetes was associated with a 56% increase in the rate of cognitive decline. Also, according to Dr. Howard, “There was a huge effect of left ventricular hypertrophy; it had the single largest impact”: Left ventricular hypertrophy was associated with a 60% increased rate of cognitive decline. No interactions by either race or sex were observed. But surprisingly, a lower educational level predicted less cognitive decline in persons with atrial fibrillation or left ventricular hypertrophy.
—Wayne Kuznar