Vascular cognitive impairment: a new approach to vascular dementia.

Vascular dementia has remained a confused concept since its origin over a century ago. Recently developed criteria, which have not met with universal acceptance, erroneously base their description of vascular dementia on Alzheimer's disease, an error that is founded in the historical confusion of the two conditions. These errors include requirements for prominent memory loss and the occurrence of a substantial degree of cognitive impairment before dementia can be diagnosed. They also treat vascular dementia as a single condition and fail to address the question of aetiology. Furthermore, these criteria largely ignore such data as is already available regarding vascular dementia. Vascular dementia is preventable. Thus cases need to be detected as soon as possible to avoid unnecessary deterioration. To correct these errors a new concept, that of vascular cognitive impairment, is proposed. This concept seeks to identify cognitive impairment due to cerebrovascular disease at the very earliest stage and, by identifying the aetiology, enable the institution of appropriate preventive therapy.