Is vascular cognitive impairment a useful concept?

Dementia and milder degrees of cognitive impairment are common in older age. Many causes of dementia have been described, which can be broadly divided into primary neurodegenerative, such as Alzheimer's disease, frontotemporal dementia or dementia with Lewy bodies, and those in which brain changes are secondary to trauma, stroke or infection. This dichotomous separation is conceptually sound. However, the majority of patients with dementia occurring in old age, actually suffer from a combination of neurodegenerative and vascular changes. Attempting to divide the dementia disorder dichotomously into Alzheimer's disease and vascular cognitive impairment may be inappropriate and may mislead the search for important mechanisms and delay the discovery of novel therapeutic targets.