Systematic review of probiotic dietary interventions for symptoms associated with dementia in older adults

This systematic review evaluated the efficacy of probiotics in managing dementia-related symptoms, including cognitive, emotional, psychiatric, neuropsychiatric symptoms, and functional dependency, in adults aged 50 and older. Following the PRISMA 2020 guidelines, a comprehensive search was conducted across PubMed, Scopus, Web of Science, and Cochrane Library. Eligible studies were randomized clinical trials assessing probiotic effects on dementia-related symptoms. Risk of bias was assessed using the Cochrane RoB 2 tool. Due to limited raw statistical data, a narrative synthesis was performed. Six clinical trials, comprising a total of 579 randomized participants, met all eligibility criteria. Probiotic supplementation consistently yielded cognitive improvements (e.g., global cognition, memory, executive function), particularly in individuals with pre-existing deficits like mild cognitive impairment (MCI) or Alzheimer’s disease (AD). Emotional outcomes were limited. Interestingly, patients with Parkinson’s disease experienced substantial emotional benefits despite a lack of cognitive gains. Strikingly, no eligible studies investigated neuropsychiatric symptoms or functional dependency. Methodological heterogeneity remained high. While all included trials adhered to Intention-to-Treat (ITT) principles, many relied on less robust imputation methods, like the Last observation carried forward (LOCF) method. Probiotics could be a promising adjunctive dietary intervention for cognitive decline, presenting a possible “window of opportunity” during the early and prodromal stages of neurodegeneration. Preliminary patterns suggest potential strain-specific benefits across different clinical domains. However, the field needs high-quality trials with rigorous missing data handling and a broadened focus on neuropsychiatric and functional outcomes to fully establish their therapeutic value in dementia care. Not applicable.