Abstract
Objectives
Probiotic supplementation has been linked to changes in cognitive function via the gut-brain axis (GBA). However, the current literature lacks a comprehensive review regarding this matter in the elderly population.
Method
Electronic databases including Medline (PubMed), Scopus, Embase, Web of Science, and Google Scholar were comprehensively searched for identifying studies that assessed the effects of probiotics on the cognitive function of the elderly published until July 2020. Articles were critically reviewed and if met the inclusion criteria, entered the study
Results
Among a total of 1374 studies, 10 were eligible for meta-analysis. No significant alteration was found in the cognition of the elderly (SMD=-0.04; 95% CI [- 1.07,0.98]; P = 0.93). There was a nonsignificant increase in the level of brain-derived neurotrophic factor (SMD = 0.58; 95% CI [-1.40,2.56]; P = 0.56) and a nonsignificant reduction in malondialdehyde levels (SMD=-0.44; 95% CI [-1.07,0.19]; P = 0.17). Levels of total antioxidant capacity (SMD = 39.93; 95% CI [2.92,76.95]; P = 0.03) and total glutathione (SMD = 61.51; 95% CI [12.39,110.62]; P = 0.01) significantly increased. A significant reduction was also noted in total cholesterol levels (SMD=-4.23; 95% CI [-8.32, −0.14]; P = 0.04).
Conclusion
Our study did not support the hypothesis of the positive effect of probiotics on cognitive function in the elderly population; which might be due to the heterogeneity across the studies.
Graphical Abstract
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Acknowledgements
The research protocol was approved and supported by Student Research Committee, Tabriz University of Medical Sciences (Registration Code: 62252).
Disclosure statement
The authors declare no conflicts of interest.
Statement of authorship
S.S and F.T designed the research; F.T and A.S conducted the literature searches; S.S, F.T and A.M selected the studies and screened the abstracts, selected the studies meeting the inclusion criteria; F.T and A.S assessed the study quality; F.T and S.S extracted the data; M.M and F.T performed statistical analysis; F.T drafted the initial manuscript,
S.S and A.M reviewed and revised the manuscript. All authors read and approved the final manuscript.
Data availability statement
All the data is available upon reasonable request.