Brain-derived neurotrophic factor plasma levels: relationship with dementia and diabetes in the elderly population.

The mechanisms linking diabetes and cognitive impairment/dementia, two common conditions of elderly people, are not completely known. Brain-derived neurotrophic factor (BDNF) has antidiabetic properties, and reduced circulating BDNF was associated with dementia. We investigated the relationship between plasma BDNF levels, dementia, and diabetes in a sample of 164 community-dwelling elderly individuals, including 50 participants with vascular dementia, 44 with late onset Alzheimer's disease, 23 with cerebrovascular disease not dementia, and 47 controls (C). Presence/absence of diabetes was registered; new diagnoses of diabetes were made by the American Diabetes Association criteria. BDNF plasma levels were measured by ELISA. Both diagnosis of dementia and diabetes were associated with lower BDNF plasma values compared with the respective controls; moreover, dementia and diabetes correlated with BDNF plasma levels, independent of possible confounders. A progressive reductions of BDNF plasma levels from C (383.9 ± 204.6 pg/mL), to cerebrovascular disease not dementia (377.1 ± 130.2), to vascular dementia (313.3 ± 114.8), to late onset Alzheimer's disease (264.7 ± 147.7) was observed, (late onset Alzheimer's disease vs C, p: .03; late onset Alzheimer's disease vs cerebrovascular disease not dementia, p: .002). Demented patients affected by diabetes had the lowest BDNF mean levels (264.9 pg/mL) among individuals enrolled in this sample, suggesting the existence of a "synergistic" effect of dementia and diabetes on BDNF levels.