The evaluation of serum brain‐derived neurotrophic factor and neurofilament light chain levels in patients with obstructive sleep apnea syndrome

OBJECTIVES: This study aimed to compare serum levels of brain‐derived neurotrophic factor (BDNF) and neurofilament light (NfL) chain in normal individuals and patients with mild and moderate‐severe obstructive sleep apnea syndrome (OSAS). METHODS: We enrolled 81 subjects referred to Otorhinolaryngology (Ear‐Nose‐Throat), Gazi University Faculty of Medicine, between 2017 and 2019. Based on the severity of OSAS, patients were divided into three groups: group 1 with mild OSAS (apnea‐hypopnea index [AHI] 5‐15; n = 26), group 2 with moderate‐severe OSAS (AHI > 15; n = 32), and group 3 with normal individuals (AHI scores < 5; n = 23). RESULTS: Serum NfL and BDNF levels were evaluated together with the clinical data for all subjects. Significant differences were seen in the oxygen desaturation index (ODI), apnea index, hypopnea index, sleep efficiency, and NfL levels (P < .05) between the three groups. In the moderate‐severe group, NfL levels showed a significant positive correlation with apnea index (P < .05, r = .389), hypopnea index (P < .05, r = .455), and ODI (P = .04; r = .362). CONCLUSIONS: Our findings clarify the pathophysiology of OSAS in cases of repetitive hypoxia and chronic neuronal damage. Based on our results, we recommend that in addition to BDNF, NfL should also be evaluated in different and larger patient cohorts.