Brain scans of 61 older adults (65-90), of whom 30 were cognitively healthy, 24 cognitively impaired and 7 diagnosed with dementia, found that, across all groups, both memory and executive function correlated negatively with brain infarcts, many of which had been clinically silent. The level of amyloid in the brain did not correlate with either changes in memory or executive function, and there was no evidence that amyloid interacted with infarcts to impair thinking.
Bottom line: vascular brain injury was far more important than amyloid burden for memory and executive function. The finding highlights the role of vascular injury in mild cognitive impairment.
(2013). The aging brain and cognition: Contribution of vascular injury and aβ to mild cognitive dysfunction.
JAMA Neurology. 1 - 8.