Low brain-derived neurotrophic factor levels in post-mortem brains of older adults with depression and dementia in a large clinicopathological sample

Background: Disturbances in peripheral brain-derived neurotrophic factor (BDNF) have been reported in major depressive disorder (MDD). However, there are no studies measuring BDNF levels directly in post-mortem brains of older subjects with MDD and dementia. We aimed to verify if brain BDNF levels were lower in older adults with lifetime history of MDD with and without dementia. Methods: BDNF levels of post-mortem brains from 80 community-dwelling older individuals with lifetime MDD with and without dementia were compared with levels from 80 controls without lifetime MDD. Participants with no reliable close informant, or with prolonged agonal state were excluded. Lifetime MDD was defined as at least one previous episode according to the Structured Clinical Interview for DSM (SCID). Results: BDNF levels were lower in the MDD group with dementia than in participants with dementia and without MDD as confirmed by multivariate analysis adjusted for clinical and cardiovascular risk factors (beta = - 0.106, 95%CI = - 0.204; - 0.009, p = 0.034). No difference was found in the group with MDD without dementia compared with their controls. Limitations: The retrospective assessment of a lifetime history of depression may be subject to information bias and this study only establishes a cross-sectional association between lifetime history of MDD and lower levels of BDNF in patients with dementia. Conclusions: In this community sample of older individuals, lower brain BDNF levels were found in cases with both lifetime MDD and dementia. Low BDNF levels could be a moderator to accelerated brain aging observed in MDD with dementia.