Circulating CD34-positive cells provide a marker of vascular risk associated with cognitive impairment.

Maintenance of uninterrupted cerebral circulation is critical for neural homeostasis. The level of circulating CD34-positive (CD34(+)) cells has been suggested as an index of cerebrovascular health, although its relationship with cognitive function has not yet been defined. In a group of individuals with cognitive impairment, the level of circulating CD34(+) cells was quantified and correlated with clinical diagnoses. Compared with normal subjects, a significant decrease in circulating CD34(+) cells was observed in patients with vascular-type cognitive impairment, although no significant change was observed in patients with Alzheimer's-type cognitive impairment who had no evidence of cerebral ischemia. The level of cognitive impairment was inversely correlated with numbers of circulating CD34(+) cells in patients with vascular-type cognitive impairment, but not Alzheimer's type. We propose that the level of circulating CD34(+) cells provides a marker of vascular risk associated with cognitive impairment, and that differences in the pathobiology of Alzheimer's- and vascular-type cognitive impairment may be mirrored in levels of circulating CD34(+) cells in these patient populations.