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Parkinsonism Relat Disord. 2018 Jan;46:69-73. doi: 10.1016/j.parkreldis.2017.11.334. Epub 2017 Nov 14.

Olfactory dysfunctions in drug-naïve Parkinson's disease with mild cognitive impairment.

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Department of Neurology, Korea University Ansan Hospital, Ansan, South Korea.
Department of Neurology, Korea University Ansan Hospital, Ansan, South Korea. Electronic address:
Department of Otorhinolaryngology, Soonchunhyang University College of Medicine, Bucheon, South Korea.
Department of Psychiatry, Korea University Ansan Hospital, Ansan, South Korea.



Evaluation of olfactory function is valuable for the detection of pre-motor state of Parkinson's disease (PD). PD patients have an increased risk of associated dementia and one-third of PD patients have mild cognitive impairment (MCI) at the time of diagnosis. However, the characteristics of olfactory dysfunction in PD-MCI patients are unclear. This study examined the relationship between olfactory dysfunction and cognitive function in drug-naïve PD at the time of diagnosis with the patterns of olfactory function in PD-MCI patients using the Korean version of the Sniffin' stick test II (KVSS II).


A total of 66 drug-naïve PD patients were enrolled. A neuropsychiatric assessment battery and KVSS II were performed. For the statistical analyses, univariate, multivariable linear regression and Student's t-test were used to determine the relationship between the variables and olfactory function.


Olfactory dysfunction was more prevalent in the PD-MCI group than in the PD-normal cognition (PD-CN) group. Each domains of odor threshold, discrimination, identification and total olfactory score were more impaired in the PD-MCI group than the PD-CN group. Whether cognitive impairment was single or multiple domain was not affected.


PD-MCI is more likely to be associated with severe olfactory impairment than PD-CN. There may be more extensive neurodegenerative processes affecting olfaction in PD-MCI patients. With further investigation and validation using neuropathological data, an objective olfactory function test could be used as a tool to evaluate disease progression. Further studies with prospective design investigating the prognostic value of olfactory dysfunction in PD-MCI patients are essential.


Mild cognitive impairment; Olfactory dysfunction; Parkinson's disease

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