Correlation between voice intensity and swallowing function in subjects with Parkinson's disease

People with Parkinson's Disease (PD) experience reduced voice intensity and dysphagia. Organs related to voice production and swallowing are structurally and neurologically intertwined. Thus, instrumental voice assessment may be useful in identifying voice impairments that can show swallowing disorders. Timely assessment of swallowing disorders may prevent the occurrence of malnutrition, dehydration, pneumonia, and death.

The aim of this study was to investigate the relationship between voice intensity and swallowing function in PD.

30 participants with PD were recruited. Motor disability was evaluated by the Unified Parkinson's Disease Rating Scale part III; voice intensity was assessed by PRAAT software during sustained /a/ and 1 min of monologue. The Penetration Aspiration Scale, the Dysphagia Outcome Severity Scale, and the Videofluoroscopic Dysphagia Scale were used to assess swallowing during videofluoroscopy. Spearman correlation coefficients, logistic, and linear models were used to analyze data.

Voice intensity correlated with swallowing: as voice intensity decreased, swallowing function deteriorated (Spearman coefficients from -0.42 to -0.72 across scales), and this holds even when adjusted for MDS-UPDRS motor scores. Swallowing impairment is 56 times more likely (p<0.01) when the voice intensity is below the normal cut-off score (60 dB) with a positive predictive value of 93%.

Reduction in voice intensity is indicative of a higher risk of swallowing dysfunction. Thus, an instrumental voice analysis seems to be a non-invasive, lowcost, easy-to-use tool to identify people with PD in need of an assessment to allow for timely swallowing management and reduction of complications caused by dysphagia.