Association Between Helicobacter pylori Infection and Motor Severity and Levodopa Response in Parkinson’s Disease: A Systematic Review

Introduction: Parkinson’s disease (PD) is a progressive neurodegenerative disorder frequently accompanied by gastrointestinal dysfunction. Chronic Helicobacter pylori infection has been proposed as a modifiable factor influencing motor severity and levodopa pharmacokinetics. This systematic review aimed to evaluate whether H. pylori infection is associated with worse motor outcomes or impaired levodopa response in patients with Parkinson’s disease.

Methods: A systematic review was conducted in accordance with PRISMA guidelines. PubMed/MEDLINE, Scopus, Web of Science, EMBASE, and regional databases were searched for studies published between 2010 and 2025 in English or Spanish. Eligible publications included human observational studies, interventional studies assessing H. pylori eradication, and systematic reviews or meta-analyses reporting motor severity (UPDRS-III), motor fluctuations, or levodopa response. A qualitative narrative synthesis was performed due to clinical and methodological heterogeneity across studies.

Results: Eighteen studies met our inclusion criteria, including 11 observational studies, 4 interventional eradication studies, and 3 systematic reviews/meta-analyses. Observational studies consistently reported that H. pylori-positive PD patients exhibited higher motor severity scores, increased motor fluctuations, delayed levodopa onset, and reduced daily “on” time compared with non-infected patients. Interventional studies demonstrated that successful H. pylori eradication was associated with improvements in motor fluctuations and, in some cases, reductions in UPDRS-III scores. Systematic reviews and meta-analyses supported a detrimental association between H. pylori infection and motor outcomes, although heterogeneity and moderate risk of bias were noted across included studies.

Conclusions: Available evidence suggests that Helicobacter pylori infection is associated with worse motor severity and impaired levodopa response in Parkinson’s disease. While eradication therapy appears to improve motor fluctuations, variability in study design and risk of bias limit definitive conclusions. Future well-designed randomized controlled trials and quantitative syntheses are warranted to clarify causality and inform clinical recommendations.