Live microbial interventions and cognitive and muscle outcomes in aging adults: a systematic review
In this abstract, 24 randomized placebo-controlled trials with 1,809 adults aged 60 or older on average tested probiotics, synbiotics or fecal transplantation. Pooled cognitive and handgrip signals were preliminary and sensitive to single studies; no firm efficacy conclusion is possible. [1]
Automatic summary · not editorially reviewed
The key findings
Twenty-four randomized placebo-controlled trials with 1,809 participants, mean age at least 60 years, were included qualitatively; 20 assessed cognitive and four muscle-related outcomes. [1]
The pooled Mini-Mental State Examination estimate was positive (g = 1.02; 95% CI 0.36–1.68) with high heterogeneity (I = 90.84%). [1]
Excluding Qaisar et al. attenuated the handgrip estimate to non-significance (g = 0.23; 95% CI −0.27 to 0.73), and no eligible fecal transplantation trial was found. [1]
The source at a glance
- Study type / format
- Systematic review and meta-analysis of randomized placebo-controlled trials (abstract).
- Population / context
- Aging adults in included trials, with a mean age of at least 60 years.
- Summary based on
- Study abstract
- Original publication
- September 16, 2026
Trials in adults aged 60 or older on average
The review asked whether live microorganism-based interventions affect cognitive and muscle-related outcomes in aging adults. It included randomized placebo-controlled trials of probiotics, synbiotics or fecal microbiota transplantation in populations with a mean age of at least 60 years. Four databases were searched, and the protocol was registered in advance. Twenty-four trials with 1,809 participants were included qualitatively: 20 assessed cognitive outcomes and four assessed muscle-related outcomes. Eleven unique studies contributed to at least one meta-analysis.
Supporting source [1]
Pooled cognitive and handgrip estimates
For Mini-Mental State Examination scores the pooled estimate was positive (g = 1.02; 95% CI 0.36–1.68), with high heterogeneity (I = 90.84%). In exploratory post hoc subgroups the estimate was positive in Alzheimer's disease (g = 1.46; 95% CI 1.14–1.79) but not statistically significant in broader cognitive impairment (g = 0.49; 95% CI −0.78 to 1.77); the subgroup difference was not significant (p = 0.15). The Repeatable Battery for the Assessment of Neuropsychological Status result was not statistically significant (g = 0.46; 95% CI −0.50 to 1.41). Handgrip strength showed a modest positive estimate (g = 0.46; 95% CI 0.06–0.85).
Supporting source [1]
Sensitivity analyses and limits of the evidence
Excluding both Akhgarjand et al. intervention arms left a positive Alzheimer's disease estimate (g = 1.63; 95% CI 1.21–2.06), but only two studies remained. Excluding Qaisar et al. attenuated the handgrip estimate to non-significance (g = 0.23; 95% CI −0.27 to 0.73). The authors describe preliminary short-term functional signals; the small evidence base, high cognitive heterogeneity, short follow-up and sensitivity to individual studies preclude firm efficacy conclusions. Subgroup and two-study sensitivity findings are exploratory. No eligible fecal transplantation trial was found, so evidence comes only from probiotic and synbiotic studies.
Supporting source [1]
How to interpret this
This explainer is based only on the abstract; the full text was not reviewed. Design details, follow-up length and outcome definitions beyond those reported are not available here. Subgroup and two-study sensitivity results are exploratory, and the evidence covers only probiotic and synbiotic studies.
Based on the study abstract; the full paper, tables and supplementary data were not reviewed.
Source & supporting passages
Silva-Olivares F, Vidal N, Acevedo-Hernández P, Rabbia V, Petermann-Rocha F, Thomas-Valdés S, Jorquera G. · europepmc.org · September 16, 2026