Stroke accelerates cognitive decline

By Eleanor McDermid, Senior medwireNews Reporter

A study of cognitive trajectories before and after stroke shows that patients experience an acute reduction, but also an accelerated long-term decline.

The findings, which appear in JAMA, reveal that global cognition was affected both acutely and in the long term, whereas new learning and verbal memory had only acute declines and executive function was affected only in the long term.

“Even though some of the results of the statistical analysis show only modest, average cognitive loss, these findings may be interpreted as clinically meaningful because few persons can afford to lose cognitive capacity over time”, write editorialists Philip Gorelick and David Nyenhuis, both from Michigan State University College of Human Medicine in Grand Rapids, USA.

Moreover, the 95% confidence intervals for the magnitude of the some of the cognitive declines extended to as much as a 0.5 standard deviation reduction, which is regarded as clinically important.

The research was conducted in the Reasons for Geographic and Racial Differences in Stroke (REGARDS) cohort. Study participants completed the Six-Item Screener (SIS) annually and a battery of three cognitive tests every second year, giving Deborah Levine (University of Michigan, Ann Arbor, USA) and colleagues the opportunity to compare cognitive trajectories in participants before and after stroke.

Not counting participants with stroke or cognitive impairment at baseline, 515 had a stroke during follow-up. In these people, global cognition on the SIS declined by a significant average of 0.10 points between pre- and post-stroke assessments. New learning, measured on the Word List Learning, declined by 1.80 points and verbal memory on the Word List Delayed Recall declined by 0.60 points.

There was no acute reduction in executive function, measured on the Animal Fluency Test, but the average decline over time increased significantly from 0.31 points per year before stroke to 0.90 points per year after stroke. Change in global cognition over time was also adversely affected by stroke, changing from an increase of 0.021 points per year to a decrease of 0.035 points per year.

“Our findings suggest a scientific need to determine whether the acute and also accelerated long-term cognitive decline are the result of incomplete rehabilitation from the initial stroke, subsequent vascular injury attributable to uncontrolled risk factors, behavioral changes, or other mechanisms”, say Levine et al.

They also suggest that stroke survivors may “warrant monitoring for mounting cognitive impairment over the years after the event.”

In their editorial, Gorelick and Nyenhuis suggest the Montreal Cognitive Assessment as a tool that is “valid, easy to administer, and highly sensitive” for screening stroke survivors and other at-risk individuals. They say the information gained from such screening can be used to plan daily patient management, including treatment of vascular risk factors.

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