The influence of age and approaching death on the course of nondopaminergic symptoms in Parkinson's disease

Predictability of inter-regional cerebral perfusion similarity on dopamine responsiveness and the moderation role of cognition in PD patients

BACKGROUND

Large heterogeneity can be found in dopamine responsiveness of patients with Parkinson's disease (PD). Instantly and objectively understanding dopamine responsiveness of patients may help clinical practice.

PURPOSE

This PD study explored the predictability of off-state inter-regional cerebral blood flow (CBF) perfusion similarity on patient's dopamine responsiveness and tested whether the predictive power could be moderated by patient's cognitive status.

MATERIALS AND METHOD

The PD cohort with 192 patients (containing off state and on state (PD-off and PD-on)) and the normal control (NC) cohort with 92 subjects were included. The intra-individual CBF relative variation networks were constructed and compared between PD-off and PD-on, PD-off and NC to identify the alterations caused by dopamine depletion. Based on that, regression analysis of off-state inter-regional CBF perfusion similarity on patient's dopamine responsiveness was performed. Finally, moderation analysis was conducted to test the moderation role of cognition on the regression model.

RESULTS

In the PD-off cohort, a total of 82 edges in the network were identified that affected by dopamine depletion. Off-state inter-regional CBF perfusion similarity was found that had a significant influence on patient's dopamine responsiveness. Cognitive status was validated that positively moderated the relationship between off-state inter-regional CBF perfusion similarity and dopamine responsiveness.

CONCLUSION

Dopamine responsiveness of PD patient could be predicted by off-state inter-regional CBF perfusion similarity. Patient's cognitive status might have a positive moderation effect on his/her dopamine responsiveness.

Sicca Symptoms in Parkinson's Disease: Association with Other Nonmotor Symptoms and Health-Related Quality of Life

Background

Frequently used nonmotor scales do not cover all aspects of dysautonomia in Parkinson's disease (PD). This study explores the association between autonomic symptoms and sicca symptoms with other nonmotor symptoms and health-related quality of life (QoL) in PD.

Methods

Autonomic symptoms (Survey of Autonomic Symptoms, SASs), motor function (Movement Disorder Society-sponsored revision of the Unified Parkinson's Disease Rating Scale III, MDS-UPDRS III), nonmotor symptoms (nonmotor symptoms questionnaire, NMS-Quest), and QoL (PD Questionnaire-39, PDQ-39) were analysed in 93 PD patients without dementia. Multivariable and multivariate analyses were performed to study the association between clinical parameters and PDQ-39 domains.

Results

Among the autonomic symptoms, sicca symptoms (xerostomia and dry eyes) were the most commonly reported (69%), followed by sexual dysfunction in men, leaking of urine, vasomotor dysfunction, constipation, sudomotor dysfunction, and orthostatic symptoms. The autonomic symptom burden (SAS total) correlated with the NMS-Quest and Hoehn and Yahr stage, but not with age, levodopa equivalent daily dose, disease duration, and the MDS-UPDRS III. The SAS total score was an independent predictor of the PDQ-39 summary index and mainly affected the PDQ-39 cognition and emotional well-being domains. Sicca symptoms were not associated with age, MDS-UPDRS III, disease duration, Hoehn and Yahr stage, and levodopa equivalent daily dose but aggravated the PDQ-39 domains: cognition, emotional well-being, bodily discomfort, and mobility. Sicca symptoms frequently occur together with other nonmotor symptoms, namely, urine urgency, orthostatic problems, and concentration problems. Overall, 75% of the subjects took at least one drug that can cause sicca symptoms (anti-PD medication, antidepressant drugs, antihypertensive drugs, antipsychotic drugs, antimuscarinic drugs, and analgesic drugs).

Conclusion

Sicca symptoms are common in PD and negatively influence QoL. The observed association between sicca symptoms and other nonmotor symptoms provides further preliminary evidence for the growing recognition of different nonmotor clusters in PD.

Peripheral mitochondrial function correlates with clinical severity in idiopathic Parkinson's disease

Background

Parkinson's disease is an intractable disorder with heterogeneous clinical presentation that may reflect different underlying pathogenic mechanisms. Surrogate indicators of pathogenic processes correlating with clinical measures may assist in better patient stratification. Mitochondrial function, which is impaired in and central to PD pathogenesis, may represent one such surrogate indicator.

Methods

Mitochondrial function was assessed by respirometry experiment in fibroblasts derived from idiopathic patients (n = 47) in normal conditions and in experimental settings that do not permit glycolysis and therefore force energy production through mitochondrial function. Respiratory parameters and clinical measures were correlated with bivariate analysis. Machine‐learning‐based classification and regression trees were used to classify patients on the basis of biochemical and clinical measures. The effects of mitochondrial respiration on α‐synuclein stress were assessed monitoring the protein phosphorylation in permitting versus restrictive glycolysis conditions.

Results

Bioenergetic properties in peripheral fibroblasts correlate with clinical measures in idiopathic patients, and the correlation is stronger with predominantly nondopaminergic signs. Bioenergetic analysis under metabolic stress, in which energy is produced solely by mitochondria, shows that patients’ fibroblasts can augment respiration, therefore indicating that mitochondrial defects are reversible. Forcing energy production through mitochondria, however, favors α‐synuclein stress in different cellular experimental systems. Machine‐learning‐based classification identified different groups of patients in which increasing disease severity parallels higher mitochondrial respiration.

Conclusion

The suppression of mitochondrial activity in PD may be an adaptive strategy to cope with concomitant pathogenic factors. Moreover, mitochondrial measures in fibroblasts are potential peripheral biomarkers to follow disease progression. © 2019 The Authors. Movement Disorders published by Wiley Periodicals, Inc. on behalf of International Parkinson and Movement Disorder Society.

Evidence for dopaminergic axonal degeneration as an early pathological process in Parkinson's disease

Parkinson's disease is a common neurodegenerative disorder presenting with a variety of motor and non-motor symptoms. The motor symptoms manifest as a result of the progressive degeneration of midbrain dopaminergic neurons. The axons of these neurons project to the striatum as the nigrostriatal pathway, which is a crucial part of the basal ganglia circuitry controlling movement. In addition to the neuronal degeneration, abnormal intraneuronal α-synuclein protein inclusions called Lewy bodies and Lewy neurites increase in number and spread throughout the nervous system as the disease progresses. While the loss of midbrain dopaminergic neurons is well-established as being central to motor symptoms, there is an increasing focus on the timing of nigrostriatal degeneration, with preclinical evidence suggesting that early axonal degeneration may play a key role in the early stages of Parkinson's disease. Here we review recent evidence for early midbrain dopaminergic axonal degeneration in patients with Parkinson's disease, and explore the potential role of α-synuclein accumulation in this process, with a focus on studies in human populations at the imaging, post-mortem, cellular and molecular levels. Finally, we discuss the implications of this for neurotrophic factor therapies for Parkinson's disease.

Differential item functioning in the Unified Dyskinesia Rating Scale (UDysRS)

OBJECTIVE

Test if differential item functioning due to gender, age, race/ethnicity, or education impacts Unified Dyskinesia Rating Scale scores.

BACKGROUND

Testing rating scales for differential item functioning is a core validation step. If differential item functioning exists, interpretation of item scores must consider secondary influences on dyskinesia ratings.

METHODS

Using Unified Dyskinesia Rating Scale translation databases (N = 3,132), we tested uniform and nonuniform differential item functioning. We required confirmation by two independent methods and considered differential item functioning pertinent if McFadden pseudo R² magnitude statistics exceeded negligible ratings.

RESULTS

No age, race/ethnicity, or education nonuniform differential item functioning was identified. Gender nonuniform differential item functioning occurred for 2 items, both with negligible magnitude. Gender, race, and education uniform differential item functioning was observed for multiple items, all with negligible magnitude.

CONCLUSIONS

The Unified Dyskinesia Rating Scale items effectively capture dyskinesia severity without pertinent gender, age, race/ ethnicity, or education influence. © 2017 International Parkinson and Movement Disorder Society.

Impact of autonomic dysfunctions on the quality of life in Parkinson's disease patients

Autonomic dysfunctions are part of a spectrum of non-motor symptoms in Parkinson's disease (PD) patients. The aim of the study was to assess the prevalence of autonomic dysfunctions and their influence on the quality of life (QoL) in PD patients, adjusted for age, sex, disease duration and motor symptoms. Patients were evaluated for motor function (Unified Parkinson's Disease Rating Scale, UPDRS part III), disease stage (Hoehn and Yahr scale, H&Y scale), autonomic dysfunction (Scales for Outcomes in Parkinson's disease, Autonomic, SCOPA-AUT) and QoL (Parkinson's Disease Questionnaire-39, PDQ-39). Urinary, gastrointestinal and sexual autonomic dysfunctions were most frequently reported, while the most severe symptoms were reported for sexual and urinary systems. Age and motor symptoms did not correlate with autonomic dysfunction, while disease duration correlated with cardiovascular dysfunction. There were sex differences on the thermoregulation subscale. All types of autonomic dysfunction influenced QoL, mostly gastrointestinal and thermoregulatory dysfunctions, except for sexual one. Many aspects of QoL (activity of daily living, emotion, cognitive functions, communication and social support) except for stigma and mobility were affected by autonomic dysfunctions. Age, disease duration, sex and motor symptoms were not found to affect global QoL scores, but had detrimental effects on different PDQ-39 dimensions. Autonomic dysfunctions influence QoL in more aspects than motor symptoms, age, disease duration and sex. Patients tend to be more stigmatized with motor than non-motor symptoms.

Gender-, age-, and race/ethnicity-based differential item functioning analysis of the movement disorder society-sponsored revision of the Unified Parkinson's disease rating scale

OBJECTIVE

Assess MDS-UPDRS items for gender-, age-, and race/ethnicity-based differential item functioning.

BACKGROUND

Assessing differential item functioning is a core rating scale validation step. For the MDS-UPDRS, differential item functioning occurs if item-score probability among people with similar levels of parkinsonism differ according to selected covariates (gender, age, race/ethnicity). If the magnitude of differential item functioning is clinically relevant, item-score interpretation must consider influences by these covariates. Differential item functioning can be nonuniform (covariate variably influences an item-score across different levels of parkinsonism) or uniform (covariate influences an item-score consistently over all levels of parkinsonism).

METHODS

Using the MDS-UPDRS translation database of more than 5,000 PD patients from 14 languages, we tested gender-, age-, and race/ethnicity-based differential item functioning. To designate an item as having clinically relevant differential item functioning, we required statistical confirmation by 2 independent methods, along with a McFadden pseudo-R² magnitude statistic greater than "negligible."

RESULTS

Most items showed no gender-, age- or race/ethnicity-based differential item functioning. When differential item functioning was identified, the magnitude statistic was always in the "negligible" range, and the scale-level impact was minimal.

CONCLUSIONS

The absence of clinically relevant differential item functioning across all items and all parts of the MDS-UPDRS is strong evidence that the scale can be used confidently. As studies of Parkinson's disease increasingly involve multinational efforts and the MDS-UPDRS has several validated non-English translations, the findings support the scale's broad applicability in populations with varying gender, age, and race/ethnicity distributions. © 2016 International Parkinson and Movement Disorder Society.

Cognitive function in 1736 participants in NINDS Exploratory Trials in PD Long-term Study-1

INTRODUCTION

Clinical cohort studies suggest that mild cognitive impairment (MCI) is common in early Parkinson's disease (PD). The objectives of this paper were to describe cognitive function in a large clinical trial of early treated PD patients at baseline and over time using two brief cognitive screening tests.

METHODS

In total 1741 participants were enrolled in the NINDS Exploratory Trials in Parkinson's disease (NET-PD) Long-term Study-1 (LS-1). The Symbol Digit Modalities Test (SDMT) was collected annually. The SCales for Outcomes in PArkinson's disease-COGnition (SCOPA-COG) was collected at baseline and at year 5. The trial was stopped early based on a planned interim analysis after half the cohort completed 5 years of follow-up. The median length of follow-up was 4 years (range 3-6 years). Predictors of cognitive change were examined using cross sectional (baseline) and longitudinal multivariable linear regression.

RESULTS

The mean (SD) change from baseline to 5 years was -1.9 (5.1) for the SCOPA-COG and -2.1 (11.1) for the SDMT. Age and baseline UPDRS motor scores were associated with a more rapid decline in SDMT scores and 5 year SCOPA-COG scores. Male gender was associated with more rapid decline in SDMT. Self-reported income was a novel predictor of baseline cognitive function, even adjusted for educational status, although not significantly associated with change over time.

CONCLUSION

This large prospective cohort study demonstrated mild cognitive decline in early treated Parkinson's disease. The study identified income level as a novel predictor of cognitive function.