Stroke Predictors May Signal Cognitive-Impairment Risk

Researchers at the University of Indiana School of Medicine have reported their latest findings about the relationship between stroke and cognitive decline.

In March, Frederick Unverzagt, Ph.D., an associate professor in the Department of Psychiatry at Indiana University School of Medicine, and colleagues reported that regional disparities in cognitive decline mirror regional disparities in stroke mortality, suggesting shared risk factors for these adverse outcomes.

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Now they’ve confirmed that cardiovascular abnormalities that predict the future occurrence of stroke also predict the development of clinically significant cognitive dysfunction.

Their findings, which are reported in the November Neurology, came from the Reasons for Geographic and Racial Differences in Stroke (REGARDS) study, an epidemiological study following a national cohort of 30,239 adults aged 45 or older, recruited from 2003 to 2007. The group was 42 percent African American; 55 percent were female.

Over half of the cohort—56 percent— were residents of the Stroke Belt, that region of the southeastern United States first described in 1965 as having 50 percent higher stroke-mortality rates than the rest of the country, and consisting of North Carolina, South Carolina, Georgia, Alabama, Mississippi, Tennessee, Arkansas, and Louisiana.

The participants’ global cognitive status was assessed annually by telephone with the Six-Item Screener (SIS) and every two years with fluency and recall tasks. The SIS is a global measure of cognitive status that assesses three-item recall and orientation to year, month, and day of the week. Scores range from 0 to 6, with a score of 4 or fewer correct items indicative of cognitive impairment. Participants who reported no stroke history and who were cognitively intact at enrollment (SIS score greater than 4) were included.

Regional differences in incident cognitive impairment (SIS score of 4 or under) were adjusted for age, sex, race, education, and time between first and last assessments. After REGARDS participants were excluded due to anomalous data, self-reported stroke at baseline, cognitive impairment at baseline, missing SIS assessments, and incident stroke prior to first SIS, 23,752 participants remained; 196 of them suffered incident stroke during the follow-up period.

The researchers also assessed participants’ Framingham Stroke Risk Profile (FSRP), which incorporates age, systolic blood pressure, presence of diabetes mellitus, current cigarette smoking, history of heart disease, atrial fibrillation, left ven tricular hypertrophy (LVH), and the use of antihypertensive medication.

Previous studies have shown that high FSRP scores are related to lower cognitive function among stroke-free individuals, but have not investigated the FSRP’s predictive value.

Results showed that in this national sample that was stroke-free and cognitively normal at baseline, the FSRP score was linearly related to the rate of cognitive impairment. In the highest FSRP quartile, almost 15 percent of participants developed cognitive impairment during the four-year follow-up period.

“All of the elements of the FSRP are significant predictors of cognitive impairment individually, and the more individual risk factors a person has, the greater the risk of cognitive impairment,” wrote Unverzagt and colleagues. “Overall it appears that the total FSRP score and its components, while initially derived to predict stroke, are also useful in the prediction of cognitive impairment.”

The researchers suspect that “subclinical cerebrovascular disease, including white matter abnormalities, silent cerebral infarction, and brain atrophy” may underlie the association they identified between stroke risk factors and cognition.

Unverzagt cited previous studies that have investigated the presence of cerebral infarcts in patients who have not shown clinical signs of stroke and told Psychiatric News that “a small substudy of the REGARDS population is being planned that will include magnetic resonance imaging of the brain and may inform us on this question.”

In the interim, Unverzagt and his colleagues suggested that “increased attention to prevention and treatment of high blood pressure may be effective in preserving cognitive health, as well as in preventing stroke.”

The study was funded by the National Institute of Neurological Disorders and Stroke, National Institutes of Health, and Department of Health and Human Services.

An abstract of “Vascular Risk Factors and Cognitive Impairment in a Stroke-Free Cohort” is posted at <www.ncbi.nlm.nih.gov/pubmed/22067959>.