Impact of olfactory function on the trajectory of cognition, motor function, and quality of life in Parkinson's disease

Chia-Yen Lin; Yu-Shan Tsai; Ming-Hong Chang

doi:10.3389/fnagi.2024.1329551

Impact of olfactory function on the trajectory of cognition, motor function, and quality of life in Parkinson's disease

Front Aging Neurosci. 2024 Mar 4:16:1329551. doi: 10.3389/fnagi.2024.1329551. eCollection 2024.

Authors

Chia-Yen Lin¹, Yu-Shan Tsai¹, Ming-Hong Chang^{1

2}

Affiliations

¹ Department of Neurology, Neurological Institute, Taichung Veterans General Hospital, Taichung, Taiwan.
² Department of Post-Baccalaureate Medicine and Brain and Neuroscience Research Center, College of Medicine, National Chung Hsing University, Taichung, Taiwan.

Abstract

Background: Olfactory dysfunction in Parkinson's disease (PD) is associated with more severe phenotypes, but trajectories of cognitive function, disease severity, and subdomains of quality-of-life measurements in patients with distinct olfactory profiles remain underexplored.

Objective: To analyze the influence of olfaction on trajectories of clinical parameters in patients with PD.

Design: Retrospective cohort study.

Subjects: From October 2016 to May 2021, the study tracked 58 participants over 3 years. Participants completed follow-up assessments using tools including the Chinese version of the University of Pennsylvania's Smell Identification Test (UPSIT), Montreal Cognitive Assessment (MoCA), Movement Disorder Society-sponsored revision of the Unified Parkinson's Disease Rating Scale, and the Chinese translation of the 39-item Parkinson's Disease Questionnaire (PDQ-39).

Methods: Participants were divided into anosmia (UPSIT < 19) and non-anosmia (UPSIT ≥ 19) groups based on initial scores. Generalized estimating equations and repeated measures correlations were used to examine longitudinal associations and correlations between olfaction and clinical parameters.

Results: Divergent cognitive trajectories were observed between groups. The anosmia group exhibited a faster cognitive decline (adjusted B [beta coefficient] = -1.8, p = 0.012) according to the interaction effect of olfaction and time on the MoCA score. The anosmia group exhibited no longitudinal correlation between cognition and olfactory function but showed correlations with age (r_rm [coefficient of repeated measures correlation] = -0.464, p = 0.004) and disease duration (r_rm = -0.457, p = 0.005). The non-anosmia group's UPSIT scores decreased over time (B = -2.3, p = 0.005) alongside a significant correlation with motor function (r_rm = -0.479, p = 0.006).

Conclusion: The anosmia group's accelerated cognitive decline correlated with age and disease duration, but not olfactory function, suggesting a poor cognitive outcome in this population despite the lack of longitudinal correlation between cognition and olfaction. The non-anosmia group exhibited progressive olfactory degradation and notable correlations between motor function and UPSIT scores, implying pathological accumulation in the olfactory structure and basal ganglia.

Keywords: Parkinson’s disease; cognition; dysosmia; motor; olfactory dysfunction; quality of life.

Grants and funding

The author(s) declare financial support was received for the research, authorship, and/or publication of this article. Grant support from Taichung Veterans General Hospital, numbers TCVGH1113401C and TCVGH1123402C. The funding source had no role in the study design, data collection, analysis, interpretation of data, writing of the report, or the decision to submit the article.