Serum Neurotrophic Factor Levels and Their Association with Cognitive Performance and Disease Severity in Alzheimer’s Disease

Background: Alzheimer's disease (AD) is a progressive, neurodegenerative disease that leads to cognitive decline. This study aimed to compare serum Brain-Derived Neurotrophic Factor (BDNF) and Nerve Growth Factor (NGF) levels between AD patients and normal controls and to evaluate correlation with cognition and the severity of the disease. Methods: This cross-sectional analytical study included 145 participants (105 patients and 40 normal controls). The Mini-Mental State Examination (MMSE) and Montreal Cognitive Assessment (MoCA) were used to measure cognitive function, and AD severity was graded as mild, moderate, or severe. Enzyme-linked immunosorbent assay (ELISA) was used to measure serum BDNF and NGF, which were correlated and tested for their diagnostic performance and associated factors of severity. Results: Serum BDNF and NGF were significantly lower in AD patients than controls (11.24 ± 3.42 vs 17.86 ± 4.11 ng/mL and 38.7 ± 11.5 vs 56.9 ± 13.2 pg/mL, respectively; both p<0.001). Both decreased from mild to severe AD (trend p<0.001). BDNF correlated with MMSE (r=0.58) and MoCA (r=0.61), while NGF correlated with MMSE (r=0.46) and MoCA (r=0.49); all p<0.001. The joint performance of BDNF and NGF showed 86.7% sensitivity and 82.5% specificity, with an AUC of 0.90. There was a positive association with severity between low BDNF, low NGF, and disease duration >5 years. Conclusion: Lower serum BDNF and NGF were correlated with worse cognition and higher severity of AD, indicating their potential as adjunctive biomarkers. Further multicenter studies should be conducted to confirm their future use for monitoring disease progression and treatment response