Decreased Plasma Brain-Derived Neurotrophic Factor Levels in Institutionalized Elderly With Depressive Disorder

Objectives To compare the differences in plasma brain-derived neurotrophic factor (BDNF) levels among institutionalized ethnic Chinese elderly participants with major depression, those with subclinical depression, and a nondepressed control group. Design A cross-sectional study. Setting The veterans' home in southern Taiwan. Participants One hundred sixty-seven residents. Measurements Questionnaires including the Minimum Data Set Nursing Home 2.1, Chinese-language version, and the short-form Geriatric Depression Scale, Chinese-language version. Depressive disorder was diagnosed by a well-trained psychiatrist using DSM-IV-TR (Diagnostic and Statistical Manual of Mental Disorders, 4th edition, text revision) criteria. We measured plasma BDNF levels in the following 3 groups: nondepressive subjects (n = 122), subclinically depressive subjects (n = 33), and subjects with major depression (n = 12). Plasma BDNF was assayed using the sandwich ELISA method. Results We noted a significantly negative association between age and plasma BDNF in the regression model. There was no significant correlation between BDNF plasma levels and body weight or platelet counts. We found that plasma BDNF was significantly lower in the major depressive group (mean, 115.1 pg/mL; SD, 57.2) than in the nondepressive group (mean, 548.8 pg/mL; SD, 370.6; P < .001). The BDNF plasma concentrations in the subclinically depressive group (mean, 231.8 pg/mL; SD, 92.4; P < .001) and control group were also significantly different. Conclusions Our findings revealed that plasma BDNF levels were reduced not only in ethnic Chinese elderly patients with major depressive disorder but also in those with subclinical depression. This makes the plasma BDNF level a potential biological marker for clinical or subclinical depression.