Effectiveness of probiotic supplements on cognitive function in mild cognitive impairment and Alzheimer's disease: A...

Cognitive impairment, encompassing mild cognitive impairment (MCI) and Alzheimer's disease (AD), poses a significant public health challenge worldwide. Emerging evidences suggest that probiotics, through modulation of the gut-brain axis, may improve cognitive function. However, their efficacy in individuals with cognitive impairment remains unclear.

This meta-analysis adhered to PRISMA guidelines, systematically reviewing randomized controlled trials (RCTs) investigating the effects of probiotics for individuals with cognitive impairment. Data were extracted from the PubMed, Embase, and Cochrane databases. Subgroup analyses were conducted based on different measurement scales (MMSE, MoCA, and RBANS), population types (cognitive impairment vs. no cognitive impairment), multiple or single strain and intervention duration. Effect sizes were expressed as standardized mean differences (SMDs) using random-effects models.

Fifteen RCTs involving 994 participants were included. Probiotic supplementation significantly improved cognitive function compared to placebo (SMD = 0.57; 95 % CI, 0.19-0.94; P = 0.003). Subgroup analyses revealed that both single-strain and multi-strain probiotics were effective; however, multi-strain probiotics demonstrated greater heterogeneity and variability in efficacy. Cognitive improvements were most pronounced with supplementation durations of at least 12 weeks (SMD = 0.73; 95 % CI, 0.30-1.16; P = 0.0009) and higher probiotic doses (>1 × 10⁹ CFU/g; SMD = 0.93; 95 % CI, 0.36-1.49; P < 0.01).

Probiotic supplementations significantly enhance cognitive function in individuals with cognitive impairment, particularly with single-strain formulations, higher doses, and a minimum duration of 12 weeks.