Stroke Risk Factors Linked to More Rapid Cognitive Decline in Elderly

Susan Jeffrey

February 29, 2008

February 29, 2008 (New Orleans, Louisiana) — A new analysis from the REGARDS cohort shows that stroke risk factors, particularly left ventricular hypertrophy (LVH), diabetes, and hypertension, are strongly related to more rapid cognitive decline, even in the absence of clinical stroke.

In this national longitudinal study, researchers found that a higher stroke risk-factor profile assessed using the Framingham Stroke Risk Score (FSRS) was strongly associated with an increased annual rate of cognitive decline.

"Differences in stroke risk can more than double the average rate of 'normal' decline," said lead author George Howard, DrPH, from the University of Alabama at Birmingham. Particular risk was seen in association with LVH, diabetes, and hypertension, suggesting although not proving that vigilance in controlling these factors may slow the rate of decline, he said.

The results were presented here at the American Stroke Association International Stroke Conference 2008.

A "Reasonable Hypothesis"

While it is "reasonable to hypothesize" that stroke risk factors contribute to cognitive decline, the literature to date is inconsistent, the authors note. To direct prevention efforts, it is important to identify which factors are most closely associated with this decline, they write.

"All of us are in a process of cognitive decline, so it's not a matter of if it's happening, but a matter of how fast it's happening," Dr. Howard said here.

To examine the relationship between stroke risk and cognitive decline, the researchers used data from the ongoing Reasons for Geographic and Racial Differences in Stroke (REGARDS) longitudinal cohort study, including some 30,000 African American and white participants aged 45 years or older recruited roughly equally from "Stroke Belt" and non–Stroke Belt geographical regions.

Cognitive function in this study is being assessed on several scales, but for this analysis they used the 6-Item Screener of global cognitive status, administered via telephone at baseline and annually during follow-up. Of the total cohort, 17,626 subjects were stroke-free at baseline and at follow-up and had at least 2 cognitive-function assessments that allowed estimation of change in function.

The relationship between traditional Framingham stroke risk factors and change in cognitive status was assessed using a mixed model approach, and the difference in annual change in the number of items answered on the screening test between subjects with and without each of the risk factors was estimated.

Overall, the average age-, race-, and sex-adjusted annual change in cognitive score — that is, the number of items correctly answered — was -0.059 items.

They found that those with a higher risk for stroke as assessed by the FSRS had a significantly more rapid decline in cognitive performance. For each 10% increase in FSRS risk, there was an additional annual decline of 0.028 items, or about 50% higher loss than the average annual loss seen in the overall group.

Significant correlations with more rapid cognitive decline were seen with increasing systolic blood pressure, diabetes, and the presence of LVH; those with these factors had significantly faster decline that those without them.

Interestingly, there was no acceleration in cognitive decline seen for those taking antihypertensive medications, a finding that "suggests but does not prove that if you are hypertensive and controlled, then hypertension is not strongly associated with cognitive decline," Dr. Howard said.

Difference in Annual Change in Average 6-Item Score Attributable to Stroke Risk Factors

Risk Factor Estimate Standard Error P
FSRS (1 SD difference) -0.028 0.004 < .0001
Systolic BP (per 10 mm Hg change) -0.008 0.003 .015
Current BP medications -0.005 0.007 .49
Diabetes -0.019 0.009 .033
Current smoking 0.018 0.010 .077
History of heart disease -0.011 0.008 0.20
Atrial fibrillation -0.021 0.013 0.11
Left ventricular hypertrophy -0.036 0.014 .0090

Surprisingly, they did not see accelerated decline with current cigarette smoking, and the relationship actually bordered on protective, he noted. There is some evidence in the literature that nicotine may be protective from a cognitive standpoint, but "with a bad delivery vehicle," Dr. Howard said. Clearly, he added, "we're not purporting an increase in cigarette smoking to protect your brain from cognitive decline."

They also looked for interactions of these risk factors by race and sex, by the presence or absence of depression, and by education levels. They found no significant interactions by race and sex or by depression, he said. However, they did find a perplexing interaction between education levels and the heart disease risk factors of atrial fibrillation and LVH, whereby these factors appeared not to predict as much cognitive decline in those with less than high-school education as they did among those with higher levels of education. The expectation would have been slower cognitive decline in the more highly educated groups, he said. They hope to look at this interaction further in ongoing analyses.

The study is funded by the National Institute of Neurological Disorders and Stroke. Dr. Howard reports financial relationships with Bayer, Brainsgate, NTII, and Boehringer Ingelheim. Coauthors report no relevant financial disclosures.

American Stroke Association International Stroke Conference 2008: Abstract 125. Presented February 22, 2008.

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