Olfactory dysfunction is associated with motor function only in tremor-dominant Parkinson's disease

Hyposmia correlates with axial signs and gait disorder in Parkinson's disease: an Italian Olfactory Identification Test study

BACKGROUND

Olfactory dysfunction is a non-motor symptom and an important biomarker of Parkinson's disease (PD) because of its high prevalence (> 90%). Whether hyposmia correlates with motor symptoms is unclear. In the present study, we aim to investigate the relationship between olfactory impairment with both motor and non-motor features and disease variables (disease duration, stage, and severity).

METHODS

One-hundred fifty-four PD patients were evaluated. Odor identification ability was tested using Italian Olfactory Identification Test (IOIT). A comprehensive spectrum of motor and non-motor features was assessed. Cognitive function was investigated through MMSE. Patients were divided into 3 different clinical phenotypes using UPDRS-III: tremor-dominant type (TDT), akinetic-rigid type (ART), and mixed type (MXT).

RESULTS

Three of the 33 IOIT items were most frequently misidentified: basil (74.3%), coffee (66.9%), and mushroom (59.6%). Hyposmia was found in 93%. Hyposmic patients were older than controls (p = 0.01). Hoehn & Yahr (H&Y) score of 2 or greater was associated with higher probability of being hyposmic (OR = 5.2, p = 0.01). IOIT score did not significantly differ between TDT, ART, and MXT of analyzed PD patients. Performance to IOIT inversely correlated with age (p < 0.01), disease duration (p = 0.01), and H&Y score of 2 or higher (p < 0.01). Clinical features that associated with higher IOIT score were freezing of gait (FOG) (p < 0.001) and camptocormia (p < 0.05).

CONCLUSIONS

In our cohort, IOIT scores showed a positive correlation with axial motor signs, but not with non-motor symptoms. IOIT may be a useful tool not only for supporting PD diagnosis but also for providing prognostic information about motor function.

Motor dysfunction in Parkinson's patients: depression differences in a latent growth model

Objective

This study aims to utilize latent growth model (LGM) to explore the developmental trajectory of motor dysfunction in Parkinson's disease (PD) patients and investigate the relationship between depression and motor dysfunction.

Methods

Four-year follow-up data from 389 PD patients were collected through the Parkinson's Progression Marker Initiative (PPMI). Firstly, a univariate LGM was employed to examine the developmental trajectory of motor dysfunction in PD patients. Subsequently, depression levels were introduced as covariates into the model, and depression was further treated as a parallel growth latent variable to study the longitudinal relationship between motor dysfunction and depression.

Results

In the trajectory analysis of motor dysfunction, the fit indices for the quadratic growth LGM model were χ2 = 7.419, df = 6, CFI = 0.998, TLI = 0.997, SRMR = 0.019, and RMSEA = 0.025, indicating that the growth trend of motor dysfunction follows a quadratic curve rather than a simple linear pattern. Introducing depression symptoms as time-varying covariates to explore their effect on motor dysfunction revealed significant positive correlations (β = 0.383, p = 0.026; β = 0.675, p < 0.001; β = 0.385, p = 0.019; β = 0.415, p = 0.014; β = 0.614, p = 0.003), suggesting that as depression levels increase, motor dysfunction scores also increase. Treating depression as a parallel developmental process in the LGM, the regression coefficients for depression intercept on motor dysfunction intercept, depression slope on motor dysfunction slope, and depression quadratic factor on motor dysfunction quadratic factor were 0.448 (p = 0.046), 1.316 (p = 0.003), and 1.496 (p = 0.038), respectively. These significant regression coefficients indicate a complex relationship between depression and motor dysfunction, involving not only initial level associations but also growth trends over time and possible quadratic effects.

Conclusion

This study indicates a quadratic growth trajectory for motor dysfunction in PD, suggesting a continuous increase in severity with a gradual deceleration in growth rate. The relationship between depression and motor dysfunction is complex, involving initial associations, evolving trends over time, and potential quadratic effects. Exacerbation of depressive symptoms may coincide with motor function deterioration.

Olfactory Dysfunction and Long-Term Trajectories of Sleep Disorders among early Parkinson's Disease: Findings from a Longitudinal Cohort

BACKGROUND

Previous studies have suggested a connection between impaired olfactory function and an increased risk of rapid eye movement sleep behavior disorder (RBD) in individuals diagnosed with Parkinson's disease (PD). However, there is a gap in knowledge regarding the potential impact of olfactory dysfunction on the long-term patterns of sleep disorders among early PD patients.

METHODS

Data from the Parkinson's Progression Markers Initiative program included 589 participants with assessments of sleep disorders using the Epworth Sleepiness Scale (ESS) and RBD Screening Questionnaire (RBDSQ). Olfactory dysfunction at baseline was measured using the University of Pennsylvania Smell Identification Test. Trajectories of sleep disorders over a 5-year follow-up were identified using group-based trajectory modeling, and the relationship between olfactory dysfunction and sleep disorder trajectories was examined through binomial logistic regression.

RESULTS

Two distinct trajectories of sleep disorders over the 5-year follow-up period were identified, characterized by maintaining a low or high ESS score and a low or high RBDSQ score. An inversion association was observed between olfactory function measures and trajectories of excessive daytime sleepiness (odds ratio [OR] = 0.97, 95% confidence interval [CI] 0.95, 1.00, p = 0.038), after controlling for potential covariates. Similarly, olfactory function showed a significant association with lower trajectories of probable RBD (OR = 0.96, 95% CI 0.94, 0.98, p = 0.001) among early PD individuals. Consistent findings were replicated across alternative analytical models.

CONCLUSIONS

Our findings indicated that olfactory dysfunction was associated with unfavorable long-term trajectories of sleep disorders among early PD.

The greatest loss of unpleasant smells may be related to the risk of more severe PD symptoms

Background

Limited research has explored the relationship between the valence of olfactory dysfunction and PD clinical symptoms. This study aimed to investigate correlations between the emotional valence of olfactory impairment and different domains of PD symptoms.

Methods

PD patients who fulfilled the clinically probable PD diagnostic criteria of the International Parkinson and Movement Disorder Society Clinical Diagnostic Criteria for Parkinson's Disease were recruited from the Center for Parkinson and Movement Disorders at Taichung Veterans General Hospital between October 2016 and April 2022. Demographic data and serial clinical assessments were collected, including the traditional Chinese version of the University of Pennsylvania Smell Identification Test (UPSIT-TC) and Movement Disorder Society-sponsored revision of the Unified Parkinson's Disease Rating Scale (MDS-UPDRS). Thirty-five odors from the UPSIT-TC were classified into neutral, pleasant or unpleasant groups. Group comparisons, correlation analyses, and linear regression analyses were conducted to examine the relationship between olfactory impairment of UPSIT-TC odors, considering emotional valence, and MDS-UPDRS subscores across various domains.

Results

A total of 176 PD patients were recruited for analysis. Patients in the predominantly neutral/unpleasant odor impairment groups had higher MDS-UPDRS part III scores compared to those in the predominantly pleasant odor impairment group (pleasant vs. neutral vs. unpleasant odor impairment groups: 26.79 ± 13.59 vs. 35.33 ± 16.36 vs. 31.57 ± 12.37, p = 0.009). This trend was also noted in MDS-UPDRS rigidity, bradykinesia, and akinetic-rigid subscores (p = 0.003, p = 0.012, and p = 0.001, respectively). Correlation analysis revealed a weak but significant correlation between rigidity/akinetic-rigid subscores and misidentification numbers for neutral/unpleasant odors (all p < 0.05), with age, gender, LEDD, and disease duration as covariates. All significances were retained in the linear regression analysis.

Conclusion

Our results emphasize the link between olfactory impairment of specific emotional valence, neutral/unpleasant odors, and PD severity, particularly with respect to akinetic-rigid symptoms. A concise olfactory test that focuses on both neutral and unpleasant odors may offer deeper insights into PD symptoms.

Underestimated olfactory domains in Huntington's disease: odour discrimination and threshold

BACKGROUND

Olfaction has recently found clinical value in prediction, discrimination and prognosis of some neurodegenerative disorders. However, data originating from standard tests on olfactory dysfunction in Huntington's disease are limited to odour identification, which is only one domain of olfactory perceptual space.

METHOD

Twenty-five patients and 25 age- and gender-matched controls were evaluated by the Sniffin' Sticks test in three domains of odour threshold, odour discrimination, odour identification and the sum score of them. Patients' motor function was assessed based on the Unified Huntington's Disease Rating Scale.

RESULTS

Compared with controls, patients' scores of all olfactory domains and their sum were significantly lower. Besides, our patients' odour threshold and odour discrimination impairments were more frequently impaired than odour identification impairment (86 per cent and 81 per cent vs 34 per cent, respectively).

CONCLUSION

Olfactory impairment is a common finding in patients with Huntington's disease; it is not limited to odour identification but is more pronounced in odour discrimination and odour threshold.

Cerebrospinal fluid alpha-synuclein, amyloid beta, total tau, and phosphorylated tau in tremor-dominant Parkinson's disease

BACKGROUND

Protein misfolding within specific brain regions is a common characteristic of neurodegenerative diseases, such as Alzheimer's disease and Parkinson's disease (PD). Therefore, a common term often used for these disorders is "proteinopathy". Currently, there has been increasing attention toward the overlap of pathogenesis between proteinopathies.

AIMS

We aimed to explore the cross-sectional and longitudinal level of the CSF α-synuclein (α-syn), amyloid βeta (Aβ1-42), total tau (t-tau), and phosphorylated tau (p-tau) in PD subjects with tremor dominant (TD) and a non-tremor dominant (nonTD) subtype from the Parkinson Progression Markers Initiative (PPMI).

METHODS

We enrolled 411 early-stage PD patients and 187 healthy controls (HCs) from the PPMI. We compared the level of CSF biomarkers at four time points including baseline, 6 months, 1 year, and 2 years. To investigate longitudinal changes in CSF proteins within each group, we used linear mixed models.

RESULTS

The level of CSF biomarkers was significantly lower in PD patients compared to HCs at any visit. Moreover, there was no statistically significant difference in the level of CSF α-syn, Aβ1-42, t-tau, and p-tau between PD-TD and PD-nonTD. Longitudinal analysis showed significant CSF α-syn reduction after one year from baseline in PD-TD patients (P = 0.047). Also, there was a significant reduction in the level of CSF Aβ1-42 after two years in PD-nonTD patients but not HCs and PD-TD (P = 0.033).

CONCLUSION

Our results indicate that different patterns in longitudinal changes of CSF biomarkers could be due to different pathophysiological mechanisms involved in each PD motor subtype.

Prevalence and characteristics of dry eye disease in Parkinson's disease: a systematic review and meta-analysis

We investigated and characterized the prevalence of dry eye disease (DED) in Parkinson's disease (PD). PubMed and EMBASE databases were searched for relevant studies between January 1, 1979 and March 10, 2022. Quality was assessed using the Joanna Briggs Institute Critical Appraisal Checklist. Study-specific estimates were combined using the DerSimonian-Laird random-effects model. Prevalence of subjective DED symptoms in patients with PD and mean differences in blink rate, corneal thickness, tear film breakup time, and tear secretion volume on Schirmer test I were compared to those in controls. Of 383 studies, 13 (1519 patients with PD) and 12 were included in qualitative and quantitative syntheses, respectively. Meta-analysis revealed a 61.1% prevalence of subjective DED symptoms in PD and that, compared with controls, patients with PD had significantly lower blink rate, thinner corneal thickness, shorter tear film breakup time, and lower tear secretion volumes on Schirmer test I, without and with anesthesia.

Olfactory dysfunction and striatal dopamine transporter binding in motor subtypes of Parkinson's disease

BACKGROUND

Olfactory dysfunction is one of the earliest non-motor symptoms (NMS) in Parkinson's disease (PD). There are contradictory results regarding the association of olfactory dysfunction and dopamine uptake in striatal nuclei among PD patients. It has been suggested that different motor subtypes of PD vary in the disease pathophysiology and progression. Thus, we hypothesized that there might be different associations between olfactory dysfunction and striatal dopaminergic neuronal loss among three motor subtypes of PD, namely, indeterminate, postural instability and gait difficulty (PIGD), and tremor-dominant (TD).

METHODS

We recruited 162 healthy controls (HCs) and 464 drug-naïve PD patients from PPMI who underwent common PD scaling tests. Striatal binding ratios (SBRs) of DaTSCAN images in caudate and putamen nuclei were calculated. To assess the olfactory function, the University of Pennsylvania Smell Identification Test (UPSIT) was carried out.

RESULTS

The UPSIT score was significantly correlated with MDS-UPDRS part I (p value: 0.002, correlation coefficient: - 0.160), MDS-UPDRS part III (p value: 0.000, correlation coefficient: - 0.248), and SBR score in right (p value: 0.000, correlation coefficient: 0.240) and left caudate (p value: 0.000, correlation coefficient: 0.221) and right (p value: 0.000, correlation coefficient: 0.323) and left putamen (p value: 0.000, correlation coefficient: 0.335) nucleus in TD subtype. There were no significant correlations in HC, PIGD, and indeterminate subjects.

CONCLUSION

The olfactory dysfunction was correlated with dopamine transporter activity in striatal nuclei only in the TD subtype. Therefore, the olfactory dysfunction in PIGD and indeterminate subtype may not be a predictive factor for the future decrease in dopamine uptake.

Dysosmia Is a Predictor of Motor Function and Quality of Life in Patients with Parkinson's Disease

(1) Background: The correlation between dysosmia with quality of life (QoL) in patients with PD was rarely reported. The study aimed to examine the effect of dysosmia on motor function and QoL in PD. (2) Methods: This cross-sectional study, performed between October 2016 and February 2021, recorded the traditional Chinese version of the University of Pennsylvania Smell Identification Test (UPSIT), the Montreal Cognitive Assessment (MoCA), the Movement Disorder Society-sponsored revision of the Unified Parkinson’s Disease Rating Scale (MDS UPDRS), and the 39-item Parkinson’s Disease Questionnaire (PDQ-39) in patients with PD. UPSIT = 19 was applied to separate the total anosmia and non-anosmia groups. (3) Results: 243 patients with PD were recruited. The total anosmia group had higher MDS UPDRS total, part II, and part III scores than the non-anosmia group. They also had worse scores on the dimensions of activities of daily living (ADL) and cognition of the PDQ-39 than the non-anosmia group. The UPSIT score correlated MDS UPDRS part III score (p < 0.0001), PDQ-39 ADL quartile (p = 0.0202), and Dopamine transporter scan (p = 0.0082) in the linear regression. (4) Conclusions: Dysosmia in PD predicted a phenotype with defective motor function, ADL, and cognition QoL. The findings supported the olfactory transmission of α-synuclein to the cortices, substantia nigra.