Decreased serum BDNF contributes to the onset of REM sleep behavior disorder in Parkinson’s disease patients

Brain-derived neurotrophic factor (BDNF) promotes neuroprotection and neuroregeneration. BDNF enhances the survival of dopaminergic neurons and improves dopaminergic neurotransmission and motor performance in patients with Parkinson's disease (PD). However, the association between BDNF levels and rapid eye movement (REM) sleep behavior disorder (RBD) in PD patients has received limited attention.We employed the Rapid Eye Movement Sleep Behavior Disorder Questionnaire-Hong Kong version (RBDQ-HK) and the Rapid Eye Movement Sleep Behavior Disorder Screening Questionnaire (RBDSQ) for RBD diagnosis. Patients were categorized into three groups: healthy controls (n = 53), PD patients without RBD (PD-nRBD; n = 56), and PD patients with RBD (PD-RBD; n = 45). Serum BDNF concentrations, demographic information, medical history, and motor/non-motor manifestations were compared between the three groups. Logistic regression analysis was performed to identify independent factors associated with PD and RBD. P-trend analysis was used to assess the relationship between BDNF levels and the risk of PD and RBD onset. Interaction effects were analyzed between BDNF, patients' age, and gender on the risk of RBD onset in PD patients.Our findings indicate that serum BDNF levels were significantly lower in PD patients compared to healthy controls (p < 0.001). PD-RBD patients exhibited higher motor symptom scores (UPDRS III) than PD-nRBD patients (p = 0.021). Additionally, the PD-RBD group demonstrated lower cognitive function scores as measured by the Montreal Cognitive Assessment (MoCA) (p < 0.001) and Mini-Mental State Examination (MMSE) (p = 0.015). PD-RBD patients displayed significantly lower BDNF levels compared to both PD-nRBD and healthy control groups (p < 0.001). Univariate and multivariate logistic regression analyses showed that reduced BDNF levels were associated with an increased risk of RBD in PD patients (p = 0.005). P-trend analysis further confirmed the progressive relationship between decreased BDNF levels and the risk of PD and RBD onset. Furthermore, our interaction analysis highlighted the importance of monitoring younger PD patients with low serum BDNF levels for potential RBD onset.This study illustrates that decreased serum BDNF levels may be linked to the development of RBD in PD patients, highlighting the potential utility of BDNF as a biomarker in clinical practice.