Drooling in Parkinson's disease: A potential clinical marker of disease severity

Drooling is a common but underrecognized non-motor symptom in Parkinson's disease (PD), associated with impaired quality of life and aspiration risk. While often managed as a peripheral issue, it may reflect broader systemic involvement. This study aimed to evaluate the prevalence and clinical significance of drooling in PD, focusing on its relationship with motor, non-motor, cognitive, and autonomic domains.

We conducted a cross-sectional study involving 513 Japanese PD patients. Drooling severity was assessed using Item 2 of the MDS-UPDRS Part II. Motor and non-motor symptoms were evaluated using the MDS-UPDRS Parts I-IV, MMSE, MoCA-J, FAB, PDSS-2, JESS, and PDQ-39. Cardiac sympathetic innervation and dopaminergic integrity were assessed using MIBG myocardial scintigraphy and DaT SPECT, respectively. Multivariable regression analysis was performed with adjustment for age, sex, and disease duration.

Drooling was observed in 66.5 % of participants, with 28.1 % categorized as severe. Droolers had significantly worse scores in motor and non-motor assessments, poorer sleep quality and quality of life, and greater cognitive deficits. They also exhibited lower heart-to-mediastinum ratios on MIBG and reduced striatal z-scores on DaT SPECT. These associations remained significant after adjustment for covariates.

Drooling in PD is linked to broader clinical and imaging abnormalities and may reflect widespread neurodegeneration beyond oropharyngeal dysfunction. These findings support the potential utility of drooling as a clinical marker of disease severity and suggest that it warrants greater attention in both research and clinical practice.