Altered BDNF levels are associated with cognitive impairment in Parkinson's disease patients with depression

Depression and cognitive impairment are both common non-motor symptoms of Parkinson's disease (PD). Brain-derived neurotrophic factor (BDNF) may play an important role in both cognitive function and depression. In this study, we examined BDNF levels, cognitive function, and the relationship between BDNF and cognitive function in PD patients with and without depressive symptoms, which has not been reported yet.

We recruited 96 PD patients with (n = 46) and without depression (n = 50) and 102 controls and examined the Repeatable Battery for the Assessment of Neuropsychological Status (RBANS) and BDNF levels in all groups. The Zung Self-Rating Depression Scale (SDS) was used to assess the severity of depression and the Hoehn-Yahr staging test was used to assess motor abilities in PD patients.

BDNF levels were lower in patients with depressive symptoms than in patients without depressive symptoms (p<0.01). The RBANS total score and the immediate memory, language and attention scores were lower in patients with depressive than in patients without depressive (all p < 0.05). Multiple regression analysis showed that BDNF was independent contributor to immediate memory, language and RBANS total score in the patients with depressive symptoms. BDNF and SDS were independent contributors to attention, and SDS was an independent contributor to delay memory (all p < 0.001).

BDNF may be involved in the pathophysiology of PD patients with depressive symptoms. Moreover, the association between BDNF and cognitive performance only in patients with depressive symptoms suggest a close relationship in BDNF, cognition and depressive symptoms in PD patients.