Intestinal dysbiosis and its relationship to gastrointestinal symptoms in patients with Parkinson's disease. Systematic review of the literature

Abstract

Introduction. Parkinson's disease (PD) presents non-motor gastrointestinal (GI) symptoms that affect quality of life. Gut dysbiosis has been proposed to contribute to these manifestations via the gut-brain axis. Materials and methods. A systematic review was conducted following the PRISMA 2020 guidelines. Original clinical studies in humans with PD (2021–2025) from six databases were included. Methodological quality was assessed using the Newcastle–Ottawa and AMSTAR 2 algorithms. Results. Eighty-six records were identified and 10 observational studies were included. A reduction in short-chain fatty acid-producing bacteria and an increase in proinflammatory taxa were observed. These changes were associated with greater severity of GI symptoms, especially constipation. Discussion: The involvement of the gut-brain axis in the pathophysiology of Parkinson's disease has been documented, particularly in individuals presenting with gastrointestinal symptoms such as dyspepsia and intestinal dysmotility. This association is reflected in the consistent link between intestinal dysbiosis and the observed digestive disorders, highlighting the role of the gastrointestinal system in the clinical expression of the disease. Conclusions. Intestinal dysbiosis was associated with GI symptoms in PD. Multicenter studies and interventional trials are recommended to validate findings and explore therapeutic strategies.