The Relationship Between Lingual Strength and Functional Swallowing Outcomes in Parkinson's Disease

The purpose of this retrospective study was to determine whether reduced lingual strength was associated with functional swallowing outcomes in individuals with Parkinson's disease (PD). Participants (N = 42) completed evaluations of maximal lingual isometric pressure (MIP) and mean lingual swallowing pressure (MSP), and flexible endoscopic evaluations of swallowing. Regression models were used to determine the association between lingual strength and functional swallowing outcomes of airway invasion, the presence of post-swallow pharyngeal residue, and the amount of pharyngeal residue (when present). Results revealed that higher MIP (p = 0.002, OR 0.93) and higher MSP (p = 0.001 OR 0.88) were associated with less airway invasion of thin liquids. Both MIP and MSP were able to differentiate between those with and without dysphagia (MIP: AUC 0.7935, p = 0.001; MSP: AUC 0.75, p = 0.026). Neither MIP nor MSP was related to the presence of residue. However, when thin liquid oropharyngeal residue was present, both MIP (p < 0.001, OR 0.99) and MSP (p < 0.001; OR 0.98) were significantly associated with the amount of residue observed. Similarly, when thin liquid hypopharyngeal residue was present, MIP (p < 0.001, OR 0.99) and MSP (p < 0.001, OR 0.98) were associated with the amount of residue observed. These findings suggest a relationship between reduced lingual strength and worse thin liquid swallowing safety and efficiency; however, the magnitude of these effects was small. This indicates that lingual strength is one important contributing factor to functional swallowing impairments in PD and may identify those with unsafe swallowing. These findings have important clinical implications for including lingual strength in the screening, assessment, and management of dysphagia in PD.