Oral health and oral microbiota composition in patients with Parkinson's disease: a case‒control study

Parkinson's disease (PD) is associated with motor and non-motor dysfunctions that may influence oral homeostasis. An altered microbiota has been linked to PD, yet oral microbial changes remain poorly characterized. This case‒control study aimed to determine if the oral microbiota, the oral health status, and salivary secretion differ between patients with PD and matched controls.

Forty participants (20 with PD and 20 controls) underwent standardized oral examinations, neurological scoring (Hoehn & Yahr; UPDRS II-III), and measurements of unstimulated (UWS) and stimulated whole saliva (SWS) flow rates. Microbial profiling of SWS samples and dorsal tongue scrapes was performed using long-read 16S rRNA gene sequencing (V1-V8). Alpha/beta diversity and differential abundance analyses were performed.

Patients with PD exhibited significantly lower UWS flow rates, higher plaque scores, and higher prevalence of xerostomia and drooling. Dental status and gingival inflammation did not differ between the groups. Microbial richness and Shannon diversity were lower in tongue scrapes from the PD group, but not in saliva samples. Veillonella, Prevotella and Streptococcus dominated the microbiota in both groups. Fusobacterium periodonticum and pseudoperiodonticum were consistently more enriched in both saliva and tongue microbiota of patients with PD.

Patients with PD have lower UWS flow rates and a shift toward a more anaerobic, biofilm-adapted oral ecosystem, particularly on the tongue. The tongue microbiome may potentially serve as a sensitive biomarker of PD-related dysbiosis.