Serum Brain-Derived Neurotrophic Factor (BDNF) in COVID-19 Patients and its Association with the COVID-19 Manifestations.

COVID-19 is a systematic disease that frequently implies neurological and non-neurological manifestations, predominantly by inducing hypoxia. Brain-derived neurotrophic factor (BDNF) is a key factor in regulating functions of nervous and respiratory systems and has been strongly related to hypoxia. Therefore, this study planned to investigate BDNF association with the COVID-19 manifestations especially neurological impairments and the infection-induced hypoxia. We enrolled sixty-four COVID-19 patients and twenty-four healthy individuals in this study. Patients were divided into two groups, with and without neurological manifestations, and their serum BDNF levels were measured by enzyme-linked immunosorbent assay (ELISA). COVID-19 patients had significantly lower BDNF levels than healthy individuals (p = 0.023). BDNF levels were significantly lower in patients with neurological manifestations compared to healthy individuals (p = 0.010). However, we did not observe a statistically significant difference in BDNF levels between patients with and without neurological manifestations (p = 0.175). BDNF's levels were significantly lower in patients with CNS manifestations (p = 0.039) and higher in patients with fever (p = 0.03) and dyspnea (p = 0.006). Secondly, BDNF levels have a significant negative association with oxygen therapy requirement (p = 0.015). These results strongly suggest the critical association between dysregulated BDNF and hypoxia in promoting COVID-19 manifestations, particularly neurological impairments.