Objective:

 To evaluate the efficacy and safety of fecal microbiota transplantation (FMT) in Parkinson’s disease (PD) through pooled quantitative analysis of clinical outcomes.

Background:

 Altered gut microbiota composition has been implicated in PD pathogenesis via the gut–brain axis. FMT, which restores microbial homeostasis, may alleviate PD-related motor and gastrointestinal dysfunctions, but the magnitude and durability of its clinical effects remain uncertain.

Design/Methods:

A systematic review and meta-analysis of randomized and observational studies assessing FMT in PD was performed using PubMed, Embase, and Cochrane databases through September 2025. Pooled mean differences (MD) and risk ratios (RR) were calculated under random-effects models for outcomes including UPDRS II/III, PDQ-39, and Wexner constipation scores, along with gastrointestinal adverse events (AEs). Subgroup and meta-regression analyses explored moderators such as follow-up duration, sample size, and study year.

Results:

 Eight studies (n = 220) were included, comprising five RCTs and three observational cohorts. FMT significantly improved motor function (UPDRS III, MD −5.05; 95% CI −7.76 to −2.34), quality of life (PDQ-39, MD −13.95; 95% CI −24.82 to −3.08), and constipation (Wexner, MD −3.91; 95% CI −7.68 to −0.13). No significant improvement was observed in activities of daily living (UPDRS II, MD −4.20; 95% CI −8.86 to 0.46). Benefits peaked at 4 weeks but diminished by 12-24 weeks. Meta-regression revealed that larger sample size correlated with greater improvement in constipation, while longer follow-up predicted greater functional benefit (UPDRS II). Gastrointestinal AEs were generally mild, though pooled analysis showed higher overall incidence with FMT versus placebo (RR 3.12; 95% CI 1.14–8.53).

Conclusions: