Cognitive Problems May Signal Increased Stroke Risk

Megan Brooks

February 15, 2011

February 15, 2011 — In a stroke-free, population-based cohort, both lower baseline executive function and memory were associated with a higher rate of incident stroke during 4.5 years of follow-up.

The findings, from Virginia G. Wadley, PhD, director of the Dementia Care Research Program at University of Alabama at Birmingham, and colleagues, were released February 9 ahead of presentation in April at the American Academy of Neurology's 63rd Annual Meeting in Honolulu, Hawaii.

"Our study is consistent with research showing that cognitive function is correlated with stroke risk," Dr. Wadley told Medscape Medical News. "Our study was different from others in that we had prestroke test scores, and we were able to examine how these scores related to later incidence of a first stroke.

"This type of research requires a large number of participants who are willing to be studied over time because only a small portion actually will go on to experience a stroke," she added. "The participants in our study were more ethnically and educationally diverse than those in previous studies and included people from every state in the continental US."

The REGARDS Study Cohort

The findings stem the ongoing Reasons for Geographic and Racial Differences in Stroke (REGARDS) study, an observational study of risk factors for stroke in 30,239 adults 45 years and older.

The analysis was based on 14,482 participants who completed a standard executive function test (verbal fluency) and 17,859 who completed a standard memory test (word recall test) at baseline and were followed up for up to 4.5 years. The participants' average age was 67 years. All were stroke free at baseline.

During follow-up, 123 participants who had taken the verbal fluency test and 129 participants who had taken the memory test experienced a stroke.

The researchers found that those who scored in the bottom fifth on the verbal fluency test or the memory test were about 3.6 times more likely to have a stroke during follow-up than those who scored in the top fifth. The difference in stroke incidence rates between those with the bottom and top 20% of scores was 3.3 strokes per 1000 person-years. The differences remained after adjustment for age, education, race, and place of residence.

At the age of 50 years, those who scored in the bottom fifth of the memory test were 9.4 times more likely to have a stroke during follow-up than those in the top fifth, but the difference was not as large at older ages.

Table 1. Stroke Risk for Lowest vs Highest Quintile of Test Performance

Measure Hazard Ratio (95% CI)
Verbal fluency 3.63 (1.77 – 7.48)
Word recall 3.45 (1.83 – 6.52)
Word recall at the age of 50 years 9.40 (1.62 – 54.57)

CI = confidence interval

Consider Cognitive Tests

Because this was a stroke-free population at baseline, the findings are "of interest," said Joseph P. Broderick, MD, professor and chair of neurology at the University of Cincinnati Neuroscience Institute in Ohio, who was not involved in the study.

Dr. Wadley made the point that neuroimaging research has established that people who have stroke risk factors, such as chronic or severe hypertension, often have changes in the brain that can affect cognitive function.

"In our study, low cognitive scores may have served as a surrogate for white matter changes, 'silent' infarcts, or subclinical neurodegenerative disease, all of which increase the risk for stroke," she noted. "However, our study does not include neuroimaging, so we did not test this directly.

"Clinicians could consider doing brief cognitive tests in those they consider at risk for stroke," Dr. Wadley told Medscape Medical News. "In our study, the memory test was better at predicting stroke at younger ages (ages 50 to 70 years). Above the age of 70, the verbal fluency test would be preferred. There are many tests and combinations of tests available, including the standardized tests we used," she noted.

The REGARDS study is supported by the National Institutes of Health and the National Institute of Neurological Disorders and Stroke.

American Academy of Neurology 63rd Annual Meeting. Released February 9, 2011, ahead of presentation.

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