Serum Neurofilament Polypeptide Level in Patients with Bipolar Disorder and its Effect on Cognitive Functioning

Elevated neurofilaments in serum are thought to be an indicator of neurodegeneration in bipolar disorder (BD). In our study, we evaluated serum neurofilament light chain (NF-L), medium chain (NF-M) and heavy chain (NF-H) levels in manic, depressive and euthymic phases of BD by ELISA method and investigated the relationship of these levels with neuropsychological functions by CNSVS (Central Nervous System Vital Signs).

Patients with manic, depressive and remission periods, aged between 18 and 50, diagnosed with BD according to DSM-5, and healthy volunteers were included in the study. The sociodemographic-clinical data form, clinical scales and CNSVS tests were applied to the participants. Serum values of NF-L, NF-M and NF-H were measured by ELISA method.

Mean NF-L, NF-M and NF-H levels showed significant differences between the patient and control groups (p < 0.001). When neurofilament levels and neurocognitive domains were evaluated in bipolar patients; NF-M and NF-H levels showed a negative correlation with NCI, composite memory, verbal and visual memory, cognitive flexibility, executive functions, psychomotor speed.

Elevated neurofilament polypeptide levels during all stages of BD compared to controls may be an indicator of inflammatory-mediated axonal damage in bipolar patients and might be used as a biomarker for neurodegeneration in BD. CNSVS neuropsychological test battery has an important place in determining the neurocognitive dysfunctions in individuals with BD. Negative correlation detected between serum NF-M and NF-H levels and cognitive test performance might reflect the neurodegeneration related poor cognitive performance.