Exercise effects on brain and behavior in healthy mice, Alzheimer's disease and Parkinson's disease model-A systematic review and meta-analysis.
Level 5 - mechanism / opinion, no new human data
Systematic review and meta-analysis restricted to preclinical animal (mouse) models.
PubMed 31991178 · doi:10.1016/j.bbr.2020.112488
What was done
A systematic review and meta-analysis of studies published between 2008 and 2019 was conducted across Medline and Scopus to evaluate treadmill exercise effects in healthy mice and mouse models of dementia (D) and Parkinson's disease (PD). Out of 430 identified records, 103 studies comprising 1,172 mice were included. Exercise regimens typically lasted 4 to 8 weeks (range 24 hours to 32 weeks), 60 minutes per day (range 8 to 120 minutes), at speeds of 10 to 12 m/min (range 0.2 to 36 m/min). Evaluated outcomes included memory, learning, neurogenesis, BDNF, TrkB, and amyloid metrics across brain regions including the hippocampus, cortex, striatum, and whole brain.
What was found
Exercise improved learning and memory. Meta-analysis demonstrated that exercise significantly increased cerebral BDNF in healthy mice (n = 150; z = 5.8, CI 3.43–12.05, p < 0.001, I² = 94.3%), D models (n = 124; z = 4.18, CI 2.22–9.12, p < 0.001, I² = 93.7%), and PD models (n = 16; z = 4.26, CI 5.03–48.73, p < 0.001, I² = 94.8%). TrkB increased in healthy mice (n = 84; z = 5.49, CI 3.8–17.73, p < 0.001, I² = 0.0%) and PD models (n = 22; z = 3.1, CI 2.58–67.3, p < 0.002, I² = 93.8%). Neurogenesis increased in healthy mice (n = 68; z = 7.08, CI 5.65–21.25, p < 0.001, I² = 17.58%) and D models (n = 116; z = 4.18, CI 2.22–9.12, p < 0.001, I² = 93.7%). In D models, exercise enhanced amyloid clearance (n = 166; z = 7.51, CI 4.86–14.85, p < 0.001, I² = 58.72%) and reduced amyloid plaques (n = 49; z = 4.65, CI 3.94–15.3, p < 0.001, I² = 0.0%).
Why it matters
This review quantitatively pools animal data to confirm that exercise drives neurotrophic signaling, promotes neurogenesis, and reduces amyloid pathology across rodent models of neurodegeneration.
Limits
Findings are entirely derived from mouse models and cannot be directly translated to human clinical outcomes. Several pooled analyses exhibited extreme statistical heterogeneity (I² > 90%) and very small animal sample sizes (e.g., n = 16 for PD BDNF; n = 22 for PD TrkB). Data regarding neuroinflammation, oxidative stress, vascular adaptations, glucose metabolism, acute versus chronic exercise paradigms, and the durability of benefits were scarce or absent in the literature.
Cited by
- supports Exercise increases brain-derived neurotrophic factor (BDNF), which stimulates the growth of new neurons in the brain.