Predictors of drooling severity in people with Parkinson's disease

Drooling, defined as the unintentional loss of saliva from the anterior oral cavity, remains poorly understood in terms of the underlying clinical factors in people with Parkinson's disease (PwP). This study aims to clarify these factors by analyzing predictors and secondarily the correlates with the severity of drooling in PwP.

We conducted a cross-sectional study involving 42 PwP with drooling and 59 without drooling. Clinical assessments were performed, and the primary outcome was the item 2.2 Saliva and drooling of the Movement Disorder Society-Unified Parkinson's Disease Rating Scale. The Mann-Whitney test was used to compare the distribution differences in clinical variables between PwP with and without drooling. The Spearman test was used to examine correlations with drooling, and ordinal logistic regression was used to examine predictors of drooling.

PwP with drooling showed significantly greater impairments in axial signs, posture, facial expression, speech, swallowing, oromotor, motor and non-motor domains than PwP without drooling. Longer disease duration, higher disease severity, levodopa equivalent daily dose, axial signs, unstimulated salivary flow rate, and impairments in speech, posture, facial expression, swallowing, oromotor, motor and non-motor domains were significantly correlated with a higher score on the item 2.2. Male sex, poorer swallowing, oromotor and speech functions were strong predictors of higher scores on the item 2.2 Saliva and drooling.

Male PwP with swallowing disorders, oromotor and speech impairments are significantly more likely to have severe drooling. Targeted interventions aimed at these swallowing, oromotor, and speech impairments may offer promising approaches to reducing drooling severity in PwP.