Taste impairment in patients with Parkinsonism.

Background: Taste impairment is a prevalent issue among individuals with idiopathic Parkinson's disease (iPD). However, understanding taste disorders among different Parkinsonism remains incomplete. Our objective was to assess the incidence and severity of taste responses to sweet, salty, sour, bitter, and umami substances in patients with iPD, progressive supranuclear palsy (PSP), and multiple system atrophy (MSA).

Methods: Taste function was evaluated by assessing the intensity ratings of four concentrations of sweet, salty, sour, bitter, and umami in 221 healthy controls (HCs), 251 iPD patients, 156 PSP patients, and 60 MSA patients. The Kruskal-Wallis one-way analysis was employed to discern differences in taste function among groups. Logistic regression models were utilized to analyze the association between disease severity and taste function.

Results: Participants with iPD, PSP, and MSA exhibited lower total taste scores (TTS) compared to HCs (P < 0.0001, P < 0.0001, and P = 0.0002, respectively). The TTS was significantly lower in iPD patients compared to PSP and MSA patients (P = 0.0024 and P = 0.0464, respectively), with no discernible difference between PSP and MSA patients (P = 0.9998). Furthermore, in patients with iPD, both disease severity and gastrointestinal function exhibited a significant negative correlation with the TTS. However, the taste test lacked the potency to reliably distinguish iPD from PSP and MSA.

Conclusions: These research findings suggest that taste impairment emerges as a phenotype of Parkinsonism, serving as a basis for differential diagnosis and guiding dietary adjustments for patients.