Decreased Serum Brain-Derived Neurotrophic Factor (BDNF) Levels in Patients with Alzheimer's Disease (AD): A Systematic Review and Meta-Analysis

• Published in: International journal of molecular sciences Vol. 20; no. 2; p. 257
• Main Authors: Ng, Ted Kheng Siang, Ho, Cyrus Su Hui, Tam, Wilson Wai San, Kua, Ee Heok, Ho, Roger Chun-Man
• Format: Journal Article
• Language: English
• Published: Switzerland MDPI AG 10.01.2019; MDPI
• Subjects: Alzheimer Disease - blood; Alzheimer Disease - complications; Alzheimer Disease - psychology; Alzheimer's disease; Animals; BDNF; Biomarkers; Brain-derived neurotrophic factor; Brain-Derived Neurotrophic Factor - blood; Case-Control Studies; cognition; Cognitive ability; Cognitive Dysfunction - blood; Cognitive Dysfunction - psychology; Confidence intervals; Cross-Sectional Studies; Dementia; Disease; Disease Progression; Humans; Laboratories; Memory; Meta-analysis; meta-regression; mild cognitive impairment; Publication Bias; Regression analysis; Review; Serum levels; Studies; Systematic review; United States > US; Alzheimer’s disease; cognition; BDNF; meta-analysis; mild cognitive impairment; systematic review; meta-regression
• ISSN: 1422-0067; 1661-6596; 1422-0067
• DOI: 10.3390/ijms20020257

Findings from previous studies reporting the levels of serum brain-derived neurotrophic factor (BDNF) in patients with Alzheimer's disease (AD) and individuals with mild cognitive impairment (MCI) have been conflicting. Hence, we performed a meta-analysis to examine the aggregate levels of serum BDNF in patients with AD and individuals with MCI, in comparison with healthy controls. Fifteen studies were included for the comparison between AD and healthy control (HC) ( = 2067). Serum BDNF levels were significantly lower in patients with AD (SMD: -0.282; 95% confidence interval [CI]: -0.535 to -0.028; significant heterogeneity: I² = 83.962). Meta-regression identified age ( < 0.001) and MMSE scores ( < 0.001) to be the significant moderators that could explain the heterogeneity in findings in these studies. Additionally, there were no significant differences in serum BDNF levels between patients with AD and MCI (eight studies, = 906) and between MCI and HC (nine studies, = 5090). In all, patients with AD, but not MCI, have significantly lower serum BDNF levels compared to healthy controls. This meta-analysis confirmed the direction of change in serum BDNF levels in dementia. This finding suggests that a significant change in peripheral BDNF levels can only be detected at the late stage of the dementia spectrum. Molecular mechanisms, implications on interventional trials, and future directions for studies examining BDNF in dementia were discussed.