Objective: This study aimed to investigate the relationship between the relative abundance of periodontal pathogens in tongue-coating samples and clinical factors in patients with Parkinson’s disease (PD).

Background: Recent studies have suggested that periodontal bacteria, like those in the gut microbiota, are associated with neurodegenerative diseases. In particular, several studies have reported a correlation between Porphyromonas gingivalis (P. gingivalis) infection and PD. However, limited research has quantified the periodontal bacterial load in tongue coatings of PD patients and examined its relationship with clinical factors.

Method: We enrolled outpatients with PD and statistically analyzed the associations between the relative abundance of periodontal pathogens in tongue coatings and clinical background factors, including subscores of the Movement Disorder Society (MDS)-Unified Parkinson’s Disease Rating Scale (UPDRS). The relative abundance of periodontal pathogens was quantified using polymerase chain reaction for three species. Positivity for each pathogen was defined as a proportion above the third quartile relative to the total bacterial load in tongue coatings. To analyze motor symptom subtypes, we extracted data from MDS-UPDRS Part 3 and calculated separate scores based on prior studies. Severe difficulties in rigidity (items 3.3a–e), tremor (items 3.15–3.18), postural instability and gait difficulty (PIGD) (items 3.9–3.13), and limb motor function (items 3.4–3.8) were defined as subscores in the third quartile or higher.

Results: Among the 44 patients enrolled, those positive for P. gingivalis exhibited a significant association with severe difficulties in PIGD (p = 0.021). No associations were observed between other bacterial species and motor symptom subtypes. In a multivariate analysis adjusted for age, P. gingivalis positivity remained independently associated with severe PIGD (odds ratio: 5.96; 95% confidence interval: 1.03–42.4; p = 0.047).

Conclusion: A higher relative abundance of P. gingivalis in tongue coatings was associated with severe PIGD, as measured by MDS-UPDRS Part 3. Chronic inflammation triggered by P. gingivalis may contribute to PD progression, particularly in the PIGD motor symptom subtype.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/association-of-periodontal-pathogen-with-subtypes-of-motor-symptoms-of-parkinsons-disease/