Decreased Serum Brain-Derived Neurotrophic Factor (BDNF) Levels in Patients with Alzheimer's Disease (AD): A Systematic Review and Meta-Analysis.
Level 3 - non-randomized controlled study
Systematic review and meta-analysis of observational studies
PubMed 30634650 · doi:10.3390/ijms20020257
What was done
A systematic review and meta-analysis was performed to evaluate serum brain-derived neurotrophic factor (BDNF) levels across individuals with Alzheimer's disease (AD), mild cognitive impairment (MCI), and healthy controls (HC). Meta-regression was conducted to evaluate age and Mini-Mental State Examination (MMSE) scores as potential moderators.
What was found
Serum BDNF levels were significantly lower in patients with AD compared to HC across 15 studies (n = 2067; SMD: -0.282; 95% CI: -0.535 to -0.028; I² = 83.962%). Meta-regression identified age (p < 0.001) and MMSE scores (p < 0.001) as significant moderators of heterogeneity. There were no significant differences in serum BDNF levels between AD and MCI (8 studies, n = 906) or between MCI and HC (9 studies, n = 5090).
Why it matters
These results clarify conflicting literature, suggesting that significant peripheral BDNF reductions occur primarily in established Alzheimer's disease rather than during the prodromal mild cognitive impairment stage.
Limits
There was substantial heterogeneity across studies (I² = 83.962%). The included evidence is observational and cross-sectional, and the abstract does not report assay standardization, medication use, or longitudinal clinical outcomes.
Cited by
- supports Brain-derived neurotrophic factor (BDNF) levels decrease in depression and Alzheimer's disease, and increase with exercise.