TABLE 1.
The representative studies on the influences of probiotic intervention on cognitive impairment.
| Study type | Subjects | Interventions, dose, and duration | Findings | References |
|---|---|---|---|---|
| RDB-PCT | Elderly patients following non-cardiac surgery (n = 120) | Capsule containing L. acidophilus, B. longum, and Enterococcus faecalis (≥107 CFU of each strain/capsule); Two capsules/day; During their hospital stay | Reduced the plasma IL-6 and cortisol levels. Probiotic supplementation could relieve post-operative cognitive impairment after non-cardiac surgery in elderly patients | Wang et al. (2021) |
| RDB-PCT | Healthy adults with mild Cognitive Impairment (Age 50–79 years) (n = 80) | B. breve MCC1274 (1 × 1010 CFU/capsule); Two capsules/day; For 16 weeks | Slow down the mild cognitive impairment symptoms. Improved the anti-inflammatory system | Bernier et al. (2021) |
| RDB-PCT | Elderly with memory impairment and 3rd repletion value of WLMIR. (n = 93) | Limosilactobacillus fermentum A2.8 (107 or 108 CFU); For 12 weeks | 107 CFU supplemented group showed improvement in memory and visuospatial function. 107 CFU supplemented group showed improvement in memory, learning, and verbal fluency | Handajani et al. (2022) |
| RDB-PCT | Patients undergoing hip or knee arthroplasty. (Age ≥60 years) (n = 106) | L. acidophilus, B. longum and Enterococcus faecalis (>107 CFU each strain); Four capsules, twice/day; During hospital stay | Improved verbal memory domain. Aid in preventing perioperative development of POCD. | Hu et al. (2023) |
| RDB-PCT | Healthy elderly subjects (Age ≥65 years) (n = 63) | B. bifidum BGN4 and B. longum BORI (1 × 109 CFU each strain); Four capsules/day; For 12 weeks | Improved the mental flexibility test and stress score. Reduced stress and inflammation-causing gut bacteria | Kim et al. (2021) |
| RCT | Middle aged (Age 52–59 years) and older adult (Age 60–75 years) with mild cognitive impairment (n = 169) | L. rhamnosus GG (109 CFU) and Prebiotic inulin from chicory root extract (200 mg)/capsule. Two capsules/day; For 12 weeks | Reduced the abundances of Prevotella and Dehalobacterium. Improved the cognitive score | Aljumaah et al. (2022) |
| RDB-PCT | Older adults with mild cognitive impairment (Age 65–88 years) (n = 130) | B. breve MCC1274 (2 × 109 CFU); For 24 weeks | ADAS’ subscales “orientation in time” and “writing” were significantly improved. Suppressed brain atrophy progression | Asaoka et al. (2022) |
| RDB-PCT | Healthy older adults without cognitive impairment (Age 60–75 years) (n = 60) | B. longum BB68S (5 × 1010 CFU/sachet); One sachet/day; For 8 weeks | Increased the relative abundances of Cellulosilyticum, Dorea, Lachnospira, and Bifidobacterium. Decreased the relative abundances of Porphyromonas, Bilophila, Parabacteroides, Tyzzerella, Collinsella, Epulopiscium, Granulicatella, and unclassified_c_Negativicutes. RBANS score was significantly improved | Shi et al. (2022) |
| RCT | Older adults with mild cognitive impairment (Age >60 years) (n = 42) | Lactococcus lactis BioF-224, Lactococcus lactis LY-66, B. lactis CP-9, B. animalis BB-115, B. infantis BLI-02, B. lactis HNO19, L. plantarum CN 2018, L. plantarum BioF-228, L. rhamnosus Bv-77, L. rhamnosus HNO01, L. johnsonii MH-68, L. paracasei MP137, L. paracasei GL-156, L. salivarius AP-32, L. acidophilus TYCA06, L. casei CS-773, L. reuteri TSR332, L. fermentum TSF331 (>2 × 1010 CFU/g); 2g/day; For 12 weeks | The relative abundances of Haemophilus, Pantoea, Erysipelotrichaceae, Anaerostipes, Ruminococcus, Prevotellaceae, Lachnospiraceae, Muribaculaceae, Coprococcus, and Blautia were increased. Cognitive function (based on the MMSE and MCA scores) and sleep quality were improved | Fei et al. (2023) |
| RCT | Healthy adult females (Age 19–31 years) (n = 53) | L. acidophilus LA02 and B. lactis BS01 (2 × 109 CFU/capsule); For 6 weeks | No significant impact on cognition in the healthy population | Czajeczny et al. (2023) |
| RCT | Adults with active physical activity (Average age ∼64.3 years) (n = 127) | L. rhamnosus GG | No significant improvement in cognitive function | Sanborn et al. (2022) |
RDB-PCT, Randomized double-blind and placebo-controlled trial; RCT, Randomized clinical trial; CFU, Colony forming unit; WLMIR, Word List Memory Immediate Recall; POCD, Postoperative cognitive dysfunction; ADAS, Alzheimer disease assessment scale; RBANS, Repeatable Battery for the Assessment of Neuropsychological Status; MMSE, Mini-mental state examination; MCA, Montreal cognitive assessment.