Aerobic exercise and volumetric change in the human hippocampus: A meta‐analysis of randomized controlled trials in healthy older individuals
Bibliographic record
Abstract
Abstract Background There is promising, albeit equivocal, evidence that aerobic exercise training (AET) increases human hippocampal volume. The evidence is unclear, as recent randomized controlled trials (RCTs) have failed to replicate AET’s previously reported favorable effects on hippocampal volume in cognitively unimpaired older individuals. We thus conducted a meta‐analysis of RCTs investigating the effects of AET on hippocampal volume and cardiorespiratory fitness (CRF) in cognitively unimpaired, healthy older individuals. Method A meta‐analysis of RCTs that delivered AET interventions to older individuals. Inclusion criteria were: 1) cognitively unimpaired, healthy individuals aged ≥ 50; 2) AET intervention delivered for at least four weeks; 3) at least one intervention group and one control group; 4) reported data of the effects of AET on hippocampal volume. Two authors independently screened titles, abstracts, and full texts, performed data extraction and methodological quality assessment of included studies. We performed meta‐analyses with random‐effects robust variance estimation models and meta‐regression analyses to test associations between changes in CRF and hippocampal volume. The primary outcome was changes in hippocampal volume, and the secondary outcome was changes in CRF. Result Eight parent trials and one secondary outcome article were eligible. The meta‐analytic summary of 17 effect sizes indicated no significant effects of AET on hippocampal volume (SMD = 0.10, 95%CI ‐0.01 to 0.21, p = 0.073). Meta‐analysis of nine studies and effect sizes showed that AET moderately improved cardiorespiratory fitness (SMD = 0.30, 95%CI 0.12 to 0.48, p = 0.005). Improvement in CRF was not statistically associated with changes in hippocampal volume ( b SE = 0.05, SE = 0.51, p = 0.923). Methodological quality was poor in one, fair in three, good in four, and excellent in one trial. Conclusion AET did not show robust effects on hippocampal volume in cognitively unimpaired, healthy older individuals. Since AET significantly improved CRF, a lack of training fidelity is unlikely to explain our findings. The biologically still plausible favorable effects of AET on hippocampal volume in cognitively unimpaired older individuals might be masked by methodological weaknesses and the inclusion of only nine studies. Future studies need to address: the lack of harmonization of hippocampus quantification methods and insufficient power to detect meaningful changes in hippocampal volume across studies.
Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.
How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.017 | 0.045 |
| Meta-epidemiology (narrow) | 0.003 | 0.002 |
| Meta-epidemiology (broad) | 0.014 | 0.040 |
| Bibliometrics | 0.004 | 0.005 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.004 | 0.002 |
| Open science | 0.002 | 0.001 |
| Research integrity | 0.002 | 0.002 |
| Insufficient payload (model declined to judge) | 0.003 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".