Objective: The purpose of this study was to compare olfactory and taste function between early drug-naive Idiopathic Parkinson’s disease (IPD) patients with or without mild cognitive impairment (MCI).

Background: Hyposmia is well-known non-motor symptoms of Parkinson’s disease (PD), and it was reported that it is associated with cognitive decline in PD. In addition, hypogeusia was often reported as one of the non-motor symptoms. However, although the neuroanatomical substrate of taste includes nucleus tractus solitarius, dorsal motor nucleus of vagus nerve, and orbitofrontal and perisylvian cortex, hypogeusia was not evaluated in the aspect of cognitive dysfunction in PD yet. This study assessed olfactory and taste function in early IPD with normal cognition and MCI.

Method: To exclude the effect of dopaminergic drugs on taste function, we enrolled drug-naive IPD patients in this study. The participants were evaluated with Montreal Cognitive Assessment (MoCA) and Seoul Neuropsychological Screening Battery (SNSB). Patients with disease in a nasopharyngeal cavity or dementia were excluded. Olfactory function was evaluated by YSK olfactory function test kit which includes threshold, discrimination, and identification test. Taste function was evaluated by YSK taste function test kit. Threshold of sweet, bitter, salty, sour and umami taste were measured. Olfactory and taste function was compared between IPD with normal cognition (IPD-NC) group and IPD with MCI (IPD-MCI) group.

Results: 26 patients with IPD-NC and 52 patients with IPD-MCI were enrolled in this study. IPD-NC and IPD-MCI group did not show a statistical difference in mean age, sex, disease duration. MoCA score was significantly lower in IPD-MCI group than IPD-NC group (p=0.014). However, there was no significant difference in the threshold, discrimination, identification, and total score of those tests between the two groups (p>0.05). In addition, there was no significant difference in the taste function test with each five taste and total score of those tests between two groups (p>0.05). Besides, the taste function between the amnestic and non-amnestic IPD-MCI group did not show a significant difference. (P>0.05).

Conclusion: Olfactory and tas dysfunction were not different in early PD with or without MCI. But further evaluation including PD patients with advanced cognitive dysfunction would be helpful in understanding the mechanism of hypogeusia in PD.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/olfactory-and-taste-function-in-early-parkinsons-disease-with-mild-cognitive-impairment/