Olfactory Dysfunction Predicts Disease Progression in Parkinson's Disease: A Longitudinal Study

Runcheng He; Yuwen Zhao; Yan He; Yangjie Zhou; Jinxia Yang; Xiaoting Zhou; Liping Zhu; Xun Zhou; Zhenhua Liu; Qian Xu; Qiying Sun; Jieqiong Tan; Xinxiang Yan; Beisha Tang; Jifeng Guo

doi:10.3389/fnins.2020.569777

Olfactory Dysfunction Predicts Disease Progression in Parkinson's Disease: A Longitudinal Study

Front Neurosci. 2020 Dec 14:14:569777. doi: 10.3389/fnins.2020.569777. eCollection 2020.

Authors

Runcheng He¹, Yuwen Zhao¹, Yan He¹, Yangjie Zhou¹, Jinxia Yang², Xiaoting Zhou¹, Liping Zhu¹, Xun Zhou¹, Zhenhua Liu^{1

3

4}, Qian Xu^{1

3

4}, Qiying Sun^{2

3

4}, Jieqiong Tan⁵, Xinxiang Yan^{1

3

4}, Beisha Tang^{1

2

3

4}, Jifeng Guo^{1

3

4

5}

Affiliations

¹ Department of Neurology, Xiangya Hospital, Central South University, Changsha, China.
² Department of Geriatrics, Xiangya Hospital, Central South University, Changsha, China.
³ Key Laboratory of Hunan Province in Neurodegenerative Disorders, Central South University, Changsha, China.
⁴ National Clinical Research Center for Geriatric Disorders, Xiangya Hospital, Central South University, Changsha, China.
⁵ Center for Medical Genetics, School of Life Sciences, Central South University, Changsha, China.

Abstract

Background and objective: Olfactory dysfunction (hyposmia) is an important non-motor symptom of Parkinson's disease (PD). To investigate the potential prognostic value of hyposmia as a marker for disease progression, we prospectively assessed clinical manifestations and longitudinal changes of hyposmic PD patients and normosmic ones.

Methods: Olfactory function was evaluated with the Sniffin' Sticks in PD patients at baseline. One hundred five hyposmic PD patients and 59 normosmic PD patients were enrolled and followed up for 2 years. They were subsequently evaluated at baseline and during follow-up periods with neurological and neuropsychological assessments. Clinical manifestations and disease progressions were compared between hyposmic and normosmic patients. In addition, the relationship between disease progressions and olfactory function was analyzed.

Results: Our study suggested that hyposmic PD patients and normosmic ones were similar in gender, age, education levels, age of onset, disease duration, and clinical features at baseline. Hyposmic PD patients exhibited more severe Unified Parkinson's Disease Rating Scale Part II-III (UPDRS II-III) scores, higher levodopa equivalent dose (LED) needs, and poorer Mini-Mental State Examination (MMSE) score at follow-up visits compared to those in normosmic PD patients. Hyposmia also showed greater rates in the increase of LED needs, improvement of UPDRS III score, and deterioration of MMSE score. Both improvement of UPDRS III score and decline of MMSE score were associated with poorer odor identification.

Conclusion: Our prospective study demonstrated that hyposmic PD patients showed a relatively worse clinical course compared with normosmic patients. Olfactory dysfunction is a useful predictor of disease progression.

Keywords: Parkinson’s disease; cognitive impairment; disease progression; hyposmia; olfactory dysfunction.