Silent strokes contribute to memory decline
MedWire News: Both subclinical strokes and neurodegenerative changes in the hippocampus contribute to memory loss, research suggests.
Silent brain infarcts in elderly people were hitherto thought to produce declines only in processing speed and executive function, with memory problems attributed to hippocampal atrophy.
But Adam Brickman (Columbia University Medical Center, New York, USA) and colleagues thought that both processes could contribute to memory loss, "reflecting the important contribution of both the integrity of the hippocampus proper as well as the more diffuse brain networks that are a part of hippocampal projection system."
Their study findings support their hypothesis, showing that brain infarcts are associated with memory performance independently of hippocampal volume.
As described in the journal Neurology, the team studied 658 community-based participants of the Washington Heights-Inwood Columbia Aging Project, aged an average of 80 years, who underwent magnetic resonance imaging and did not have dementia at baseline. Of these, 20% had subcortical infarcts and 6% had cortical infarcts. Participants who had both cortical and subcortical infarcts were excluded from the analysis.
Around 20% of participants with brain infarcts had a history of clinical stroke, compared with 5% of those without infarcts. But most patients with infarcts had no record of clinical symptoms.
Participants with infarcts had evidence of hippocampal atrophy, with average relative hippocampal volumes (ratio of total hippocampal to intracranial volume) of 0.279 in those with cortical infarcts and 0.281 in those with subcortical infarcts, compared with 0.296 in participants with no infarcts.
This relationship was not explained by total brain atrophy or by the presence of infarcts in the arterial territory supplying the hippocampus.
Despite the association between brain infarcts and hippocampal atrophy, each factor was significantly and independently associated with memory dysfunction as assessed with the standard Selective Reminding Test.
Hippocampal volume predicted only memory function - most specifically long-term recall and delayed recognition. The presence of brain infarcts was associated with somewhat different aspects of memory function, namely learning, long-term recall, and delayed recognition, and was also associated with impaired language, executive/speed, and visuospatial functions (assessed with a battery of standard tests).
"Brain infarcts are a largely preventable brain injury, with clearly identified risk factors, and prevention programs," conclude Brickman et al. "A public health push toward emphasizing stroke prevention may significantly decrease incidence of dementia."
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By Eleanor McDermid