Fecal Microbiota Transplantation in Parkinson Disease

BACKGROUND AND OBJECTIVES: Parkinson disease (PD) is a progressive neurodegenerative disorder increasingly linked to gut microbiota dysbiosis, which may influence disease mechanisms and symptom expression. Fecal microbiota transplantation (FMT) targets the gut-brain axis, but clinical evidence remains inconsistent. This study aimed to evaluate the efficacy and safety of FMT in PD. METHODS: We conducted a systematic review and meta-analysis following Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines, with protocol registration in International Prospective Register of Systematic Reviews (CRD420251142846). MEDLINE, Embase, and the Cochrane Library were searched from inception through September 2025. Randomized controlled trials (RCTs) and observational studies enrolling adults with mild-to-moderate PD who received FMT through any administration route were eligible. The primary outcome was motor function assessed by the Unified Parkinson's Disease Rating Scale (UPDRS) part III. Secondary outcomes included UPDRS part II, quality of life (Parkinson's Disease Questionnaire-39 [PDQ-39]), constipation severity (Wexner score), and adverse events. Random-effects models pooled effect estimates with 95% CIs, and exploratory meta-regression assessed follow-up duration, publication year, and sample size. RESULTS: = 0.043). FMT was generally well tolerated; however, gastrointestinal adverse events were more frequent in the FMT group (risk ratio 3.12, 95% CI 1.14-8.53), predominantly mild to moderate. DISCUSSION: FMT may provide short-term improvements in motor and gastrointestinal symptoms in PD, but effects appear transient. Small sample sizes, heterogeneity, and limited follow-up restrict conclusions, underscoring the need for larger randomized trials. Pooled estimates reflected evidence from observational studies and should be interpreted cautiously.