Recent studies suggest strong interactions between cerebrovascular and Alzheimer's disease (AD) pathology. These conditions share common risk factors and individuals having both frequently show greater cognitive impairment than those affected by only one disease. Many studies point to early vascular dysregulations in AD. The exchange between vascular and neural cells occurs through mechanisms not completely understood, involving interactions among endothelial, glial, neuronal and smooth muscle cells within the neurovascular unit. Studies suggest that the dysregulation of the unit is likely associated with hypertension and other systemic diseases. Associations between hypertension and cognitive decline are not established, but other variables associated with hypertension could create a causal link. Many studies have lacked a consistent, quantitative neuropsychological approach for assessing cognitive functions. This approach is reductive, as the need for a formal neuropsychological assessment has gained broad recognition, and the definition of dementia has gone through revision processes, which are in progress.