Recent evidence suggests that there is clear association between microbiota and cognitive functioning, which is known as microbiome-gut-brain axis. Probiotic bacteria consumption can alter human microbiota; therefore, probiotic supplementation might affect the gut microbiota dynamics and influence cognitive function.
Three electronic databases including PubMed, ProQuest, and EBSCOHost databases were utilized. Manual hand search of article was also done. We selected randomized controlled trial articles that measure cognitive function (as the primary outcome) after intervention with probiotic supplementation on older adult population with AD, MCI, or healthy condition. The following terms and its variant were used: “probiotic,” “cognitive function,” “mild cognitive impairment,” “dementia,” and “Alzheimer’s disease.”
Nine of 10 included studies (AD, MCI, or healthy cognition population) showed cognitive function was improved significantly after probiotic supplementation, compared to control group. One study that included severe AD did not show significant changes.
Most studies involving AD, MCI, or healthy older adults showed cognitive improvement in subjects treated with probiotics for 12-24 weeks.

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