Dose- and modality-specific effects of exercise on BDNF and depression in middle-aged and older adults with mild cognitive impairment: A Bayesian network meta-analysis

To evaluate the effects of exercise modality and weekly exercise dose on peripheral brain-derived neurotrophic factor (BDNF) and depressive symptoms in middle-aged and older adults with mild cognitive impairment (MCI), and to examine the robustness of the dose-specific predictions from the primary quadratic model across alternative dose-response functions.

PubMed, Embase, Web of Science, the Cochrane Library, and APA PsycInfo were searched from inception to 13 April 2026. Randomized controlled trials involving adults aged 50 years or older with MCI and reporting BDNF or depression-related outcomes were included. Effect sizes were expressed as Hedges' g. Separate Bayesian random-effects network dose-response meta-analyses were conducted for BDNF, overall depressive symptoms, and modality-specific depressive symptoms. The quadratic model was used as the primary model to predict intervention effects at different exercise doses. Linear, Emax, and natural cubic spline models were fitted as functional-form sensitivity analyses.