Abstract / Summary
Aims: To evaluate the available evidence on the association between oral microbiota composition and Parkinson's disease (PD), including its relationship with disease severity and clinical features.
Methods and results: This systematic review was registered in PROSPERO (CRD42024560059) and conducted according to the PRISMA 2020 statement. Searches were performed in PubMed, Embase, Web of Science, LILACS, Scopus, and SciELO. Observational studies evaluating the oral microbiota of adults with PD were included. Eleven studies, predominantly case-control, were analyzed, with 16S rRNA sequencing used in 90.9% of them. The genera most frequently associated with PD were Lactobacillus (45.45%), Prevotella (36.7%), and Streptococcus (36.7%). Most studies reported differences in beta diversity, indicating a distinct oral microbial profile in patients with PD. Higher Lactobacillus abundance and lower Neisseria abundance were associated with greater disease severity and poorer cognitive performance in some studies. According to the GRADE approach, the certainty of the evidence was very low.
Conclusion: The available evidence suggests that PD is associated with alterations in oral microbiota composition. However, because the evidence is derived predominantly from observational studies, causal relationships cannot be established. Longitudinal studies using standardized microbiome methodologies are needed to validate these microbial signatures as candidate biomarkers.