Brain Blood Flow Boost Fails to Enhance Cognition

Procedures to open narrowed carotid arteries did not improve thinking or memory skills, study finds.

Feb. 4, 2026 at 11:47pm

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Procedures that remove plaque from a narrowed carotid artery in the neck or prop the artery open with a stent did not appear to be better at improving cognitive function than medications and lifestyle changes, according to a substudy of the CREST-2 trial that included more than 2,000 adults.

Why it matters

Previous research has found an association between carotid stenosis and lower performance on tests of cognitive function, but this is the first large carotid stenosis study to include cognition as a major outcome in the study design of a randomized controlled trial.

The details

The CREST-2 substudy researchers found no difference in thinking or memory over time among participants who had a procedure to restore blood flow (stenting or surgery) and those treated solely with intensive medical therapy. Even among participants with the lowest cognitive function at the start of the study, who were expected to gain the most from these treatments, there were still no differences in cognitive skills among the treatment groups.

  • The CREST-2 (Carotid Revascularization and Medical Management for Asymptomatic Carotid Stenosis) Trial compared stroke rates among people randomly selected to receive either intensive medical management alone; intensive management combined with carotid endarterectomy; or intensive management plus stenting.
  • The CREST-2 substudy included a "cognitive core" component to assess cognitive performance before treatment and yearly for up to four years.
  • The study results were published in 2021 in Stroke, the peer-reviewed scientific journal of the American Stroke Association, a division of the American Heart Association.

The players

Ronald M. Lazar

A professor of neurology and neurobiology at the University of Alabama at Birmingham (UAB) and director of the UAB McKnight Brain Institute, as well as the principal investigator of the Cognitive Core substudy and overall co-investigator of CREST-2.

Mitchell Elkind

The American Heart Association's Chief Science Officer for Brain Health and Stroke and a past volunteer president of the Association (2020-2021).

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What they’re saying

“Whether patients undergo a procedure to remove plaque in the carotid artery (carotid endarterectomy), stenting to insert a flexible tube to hold open the narrowed part of the artery, or a combination of medications and lifestyle guidance without a procedure, there should be no expectation that cognition will improve after the treatment.”

— Ronald M. Lazar, Professor of neurology and neurobiology at the University of Alabama at Birmingham (UAB) and director of the UAB McKnight Brain Institute (Stroke)

“These results from CREST-2 do not provide evidence of benefit of carotid revascularization on cognitive function among patients with significant carotid stenosis, although there is a benefit for stroke reduction. Cognitive decline associated with aging is a complex problem; however, restoration of blood flow through the large vessels alone may not be sufficient to address the many other pathways to decline, such as inflammation, neurodegeneration and small vessel disease. More research on how to mitigate cognitive decline and reduce dementia risk is needed, which is why the American Heart Association has supported study of these important areas and others.”

— Mitchell Elkind, American Heart Association's Chief Science Officer for Brain Health and Stroke and a past volunteer president of the Association (2020-2021) (Stroke)

What’s next

The study could not determine whether reduced blood flow to the brain is the sole or most important reason for cognitive decline in carotid artery disease. "Some characteristics of a blockage can cause small particles to travel to the brain. These particles may, over time, affect how the brain functions. This is an area we plan to explore in our future research," Lazar said.

The takeaway

These results suggest that restoring blood flow to the brain through procedures to open narrowed carotid arteries may not be enough to improve cognitive function in patients with carotid stenosis. More research is needed to understand the complex factors contributing to cognitive decline in this population.