Role of Respiratory Pressure in Swallowing Function and Aspiration Risk in Parkinsonism

Dysphagia is a prevalent and clinically significant non-motor symptom in Parkinson's disease (PD) and atypical parkinsonism, leading to aspiration pneumonia and increased morbidity. Respiratory muscle weakness has been suggested as a contributor to impaired airway protection, but its clinical implications in parkinsonism remain underexplored. This retrospective study investigated the association between maximal respiratory pressure and dysphagia-related outcomes in individuals with PD and atypical parkinsonism. A total of 98 cases who underwent both videofluoroscopic swallowing study (VFSS) and respiratory pressure testing within three months were included. Maximal inspiratory pressure (MIP) and maximal expiratory pressure (MEP) were measured and normalized to age- and sex-matched predicted values. Swallowing function was evaluated using the Videofluoroscopic Dysphagia Scale (VDS), Penetration-Aspiration Scale (PAS), and Swallowing Disturbance Questionnaire (SDQ). Normalized MIP and MEP were significantly lower in the aspiration group (35.39 ± 22.62%, 40.69 ± 24.75%) than in the non-aspiration group (44.50 ± 21.79%, 50.30 ± 20.85%; p < 0.05, respectively). In atypical parkinsonism, normalized MIP and MEP were significantly lower in the aspiration group and was correlated with higher VDS scores (r = - 0.320, r = - 0.426; p < 0.05) and PAS scores (r = - 0.271, r = - 0.280; p < 0.05). Logistic regression showed that in atypical parkinsonism, each 1% decrease in normalized MEP was associated with a 4.7% increase in aspiration odds (adjusted OR = 0.953, 95% CI: 0.917-0.991). These findings suggest that reduced respiratory muscle strength may be linked to impaired swallowing function in parkinsonism, especially in atypical forms. Further prospective studies are needed to validate these results and clarify the role of respiratory muscle strength in dysphagia in parkinsonism.