Cytomegalovirus is present in a very high proportion of brains from vascular dementia patients.

We previously found that herpes simplex type 1 virus (HSV1), when present in brain of carriers of the apolipoprotein E type 4 allele is a strong risk factor for Alzheimer's disease. To find if HSV1 or certain other herpesviruses are involved in vascular dementia (VaD), we searched post mortem brain specimens from patients suffering from VaD for the presence of HSV1, cytomegalovirus (CMV), and human herpesvirus type 6 DNA, using polymerase chain reaction. We have found that a very high proportion of the VaD patients, 93% (14/15), but not of age-matched normals, 34% (10/29), harbor CMV DNA (P = 0.0002); the proportions of the patients harboring the other viruses in brain do not differ significantly from those of the normals. Further studies are needed to reveal whether or not the association of CMV with VaD is causal.