Conceptual background to vascular cognitive impairment.

The current criteria for vascular dementia use a paradigm that first diagnoses dementia on the basis of Alzheimer-type criteria and then superimposes upon this vascular events and risk factors to convert a diagnosis of Alzheimer disease to one of vascular dementia. There are two fundamental flaws with this approach. First, the neuropsychological features of Alzheimer disease are not the same as those for vascular dementia and so use of the current criteria will fail to diagnose many cases, particularly those in whom memory loss is not prominent. Second, progression of vascular dementia should be modifiable by adjustment of risk factors and, possibly, by the use of neuroprotective agents. Given this, it is absurd to wait until patients are frankly demented. It is far more appropriate to detect patients at risk of developing cognitive loss as soon as possible. This could be in the earliest symptomatic stage (vascular cognitive impairment) or even prior to this (brain-at-risk) stage. New criteria, based on evidence rather than on supposition, that focus on early disease are urgently needed.