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.
Gong Cheng, Jinhui Qiu, Shengtao Li
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In 30 seconds
This Bayesian network dose-response meta-analysis examined randomized controlled trials of exercise in adults aged 50 years or older with mild cognitive impairment (MCI), assessing peripheral brain-derived neurotrophic factor (BDNF) and depressive symptoms. Across 28 studies involving 2,262 participants, exercise was associated with higher BDNF and improved depressive symptoms. In the primary quadratic model, the largest predicted effects occurred at 440 MET-min/week for BDNF (posterior mean, 0.752; 95% CrI, 0.287 to 1.249) and 670 MET-min/week for depressive symptoms (posterior mean, 0.382; 95% CrI, 0.147 to 0.674). Alternative dose-response models predicted different maxima.
Key findings
- The primary quadratic model predicted the largest BDNF effect at 440 MET-min/week (posterior mean, 0.752; 95% CrI, 0.287 to 1.249).
- For depressive symptoms, the largest quadratic-model prediction was at 670 MET-min/week (posterior mean, 0.382; 95% CrI, 0.147 to 0.674).
- Dancing and multicomponent exercise had comparatively favourable estimates at selected doses; estimates for Tai Chi, walking, and yoga were less precise.
- Sensitivity analyses using linear, Emax, and natural cubic spline models identified different dose locations for maximum predicted effects.
Why it matters
The findings suggest that exercise may benefit both peripheral BDNF and depressive symptoms in people with MCI, while the dose-response relationship may not be linear. However, the predicted dose peaks depend on the model used. Distinguishing model-based estimates from established clinical targets is important when interpreting evidence and designing future dose-ranging studies.
What to keep in mind
The dose maxima were model-predicted, and alternative dose-response functions identified different locations for peak effects; the authors therefore do not establish confirmed optimal exercise doses.