Examining the Reserve Hypothesis in Parkinson's Disease: A Longitudinal Study

Emerging perspectives on precision therapy for Parkinson's disease: multidimensional evidence leading to a new breakthrough in personalized medicine

PD is a prevalent and progressive neurodegenerative disorder characterized by both motor and non-motor symptoms. Genes play a significant role in the onset and progression of the disease. While the complexity and pleiotropy of gene expression networks have posed challenges for gene-targeted therapies, numerous pathways of gene variant expression show promise as therapeutic targets in preclinical studies, with some already in clinical trials. With the recognition of the numerous genes and complex pathways that can influence PD, it may be possible to take a novel approach to choose a treatment for the condition. This approach would be based on the symptoms, genomics, and underlying mechanisms of the disease. We discuss the utilization of emerging genetic and pathological knowledge of PD patients to categorize the disease into subgroups. Our long-term objective is to generate new insights for the therapeutic approach to the disease, aiming to delay and treat it more effectively, and ultimately reduce the burden on individuals and society.

GBA moderates cognitive reserve's effect on cognitive function in patients with Parkinson's disease

BACKGROUND

Cognitive reserve (CR) involves an individual's ability to maintain cognitive vitality over their lifespan. Glucocerebrosidase (GBA) gene mutations contribute to additional effects on cognitive function in Parkinson's disease (PD) patients, but the interplay between GBA mutations and CR remains unclear. We investigated the interactions among CR, GBA, and diseases, aiming to examine whether the CR established at different stages interacts with specific genotypes to affect cognitive function.

METHODS

Three hundred and eighteen participants' CR indicators (i.e., education, occupation, and social function) and comprehensive neuropsychological function (i.e., tests for executive function, attention/working memory, visuospatial function, memory, and language) were evaluated.

RESULTS

We found that CR established in a specific life stage influences the individual's cognitive function, particularly in PD, based on their distinct GBA rs9628662 genotypes. Attention/working memory and memory performance are affected by occupational complexity in midlife in PD patients with the GG genotype (q < 0.0001; q < 0.0001) and healthy adults with the T genotype (q = 0.0440; q < 0.0001). Language is influenced by early education and occupation, and the effects of occupation are also observed in PD patients with the GG genotype (q = 0.0040) and in healthy adults carrying the T genotype (q = 0.0040).

CONCLUSIONS

CR, established at different life stages, can be influenced by the GBA rs9628662 genotype, impacting later-life cognition. Validating genotypes and incorporating genotype information when assessing cognitive reserve effects is crucial and can enhance targeted cognitive training.

Influence of cognitive reserve on cognitive and motor function in α-synucleinopathies: A systematic review and multilevel meta-analysis

Cognitive reserve has shown promise as a justification for neuropathologically unexplainable clinical outcomes in Alzheimer's disease. Recent evidence suggests this effect may be replicated in conditions like Parkinson's disease, dementia with Lewy bodies, and multiple system atrophy. However, the relationships between cognitive reserve and different cognitive abilities, as well as motor outcomes, are still poorly understood in these conditions. Additionally, it is unclear whether the reported effects are confounded by medication. This review analysed studies investigating the relationship between cognitive reserve and clinical outcomes in these α-synucleinopathy cohorts, identified from MEDLINE, Scopus, psycINFO, CINAHL, and Web of Science. 85 records, containing 176 cognition and 31 motor function effect sizes, were pooled using multilevel meta-analysis. There was a significant, positive association between higher cognitive reserve and both better cognition and motor function. Cognition effect sizes differed by disease subtype, cognitive reserve measure, and outcome type; however, no moderators significantly impacted motor function. Review findings highlight the clinical implications of cognitive reserve and importance of engaging in reserve-building behaviours.

Structural underpinnings and long-term effects of resilience in Parkinson's disease

Resilience in neuroscience generally refers to an individual's capacity to counteract the adverse effects of a neuropathological condition. While resilience mechanisms in Alzheimer's disease are well-investigated, knowledge regarding its quantification, neurobiological underpinnings, network adaptations, and long-term effects in Parkinson's disease is limited. Our study involved 151 Parkinson's patients from the Parkinson's Progression Marker Initiative Database with available Magnetic Resonance Imaging, Dopamine Transporter Single-Photon Emission Computed Tomography scans, and clinical information. We used an improved prediction model linking neuropathology to symptom severity to estimate individual resilience levels. Higher resilience levels were associated with a more active lifestyle, increased grey matter volume in motor-associated regions, a distinct structural connectivity network and maintenance of relative motor functioning for up to a decade. Overall, the results indicate that relative maintenance of motor function in Parkinson's patients may be associated with greater neuronal substrate, allowing higher tolerance against neurodegenerative processes through dynamic network restructuring.

Proxy-analysis of the genetics of cognitive decline in Parkinson's disease through polygenic scores

Cognitive decline is common in Parkinson's disease (PD) and its genetic risk factors are not well known to date, besides variants in the GBA and APOE genes. However, variation in complex traits is caused by numerous variants and is usually studied with genome-wide association studies (GWAS), requiring a large sample size, which is difficult to achieve for outcome measures in PD. Taking an alternative approach, we computed 100 polygenic scores (PGS) related to cognitive, dementia, stroke, and brain anatomical phenotypes and investigated their association with cognitive decline in six longitudinal cohorts. The analysis was adjusted for age, sex, genetic ancestry, follow-up duration, GBA and APOE status. Then, we meta-analyzed five of these cohorts, comprising a total of 1702 PD participants with 6156 visits, using the Montreal Cognitive Assessment as a cognitive outcome measure. After correction for multiple comparisons, we found four PGS significantly associated with cognitive decline: intelligence (p = 5.26e-13), cognitive performance (p = 1.46e-12), educational attainment (p = 8.52e-10), and reasoning (p = 3.58e-5). Survival analyses highlighted an offset of several years between the first and last quartiles of PGS, with significant differences for the PGS of cognitive performance (5 years) and educational attainment (7 years). In conclusion, we found four PGS associated with cognitive decline in PD, all associated with general cognitive phenotypes. This study highlights the common genetic factors between cognitive decline in PD and the general population, and the importance of the participant's cognitive reserve for cognitive outcome in PD.

Educational level and its association with dopamine transporter loss in patients with Parkinson's disease

BACKGROUND

According to the cognitive-reserve concept, higher educated dementia patients tolerate more brain pathology than lower educated patients with similar impairment. Here, we examined whether higher education is associated with more severe dopamine terminal loss at the diagnosis of Parkinson's disease (PD).

METHODS

Dopamine transporter (DaT) SPECT information of 352 de novo PD patients and 172 healthy controls (HC) were retrieved from PPMI. Correlation analyses were performed between education years and regional DaT signal (i.e., putamen, caudate, striatum), correcting for UPDRS-III, age, sex and MoCA. Second, using a median split on education (Md = 16 yrs), high and low education groups were determined, which were matched for demographic and/or clinical scores and compared based on regional DaT signals. Finally, moderation analyses were conducted in the PD cohort, assessing the effect of education on the relation between putaminal DaT capacity and UPDRS-III. All analyses were performed across the entire cohorts and separately for three age ranges (sixth, seventh and eighth life decade).

RESULTS

Only PD patients in their eighth life decade presented a positive association between education and regional dopamine signalling. A significant moderation effect of education on the association between putaminal DaT signal loss and motor symptom severity was observed in this group (B=3.377, t=3.075, p = .003). The remaining analyses did not yield any significant results, neither in the PD nor HC cohort.

CONCLUSION

Higher education is not related with greater tolerance against dopamine loss in PD, but may nonetheless assert protective effects at more advanced age.

Multifactorial assessment of Parkinson's disease course and outcomes using trajectory modeling in a multiethnic, multisite cohort - extension of the LONG-PD study

Background

The severity, progression, and outcomes of motor and non-motor symptoms in Parkinson's disease (PD) are quite variable. Following PD cohorts holds promise for identifying predictors of disease severity and progression.

Methods

PD patients (N = 871) were enrolled at five sites. Enrollment occurred within 5 years of initial motor symptom onset. Disease progression was assessed annually for 2-to-10 years after onset. Group-based trajectory modeling was used to identify groups differing in disease progression. Models were developed for UPDRS-III scores, UPDRS-III tremor and bradykinesia-rigidity subscores, Hoehn & Yahr (H&Y) stage, Mini-Mental Status Exam (MMSE) scores, and UPDRS-III, H&Y and MMSE scores considered together. Predictors of trajectory-group membership were modeled simultaneously with the trajectories. Kaplan-Meier survival analysis evaluated survival free of PD outcomes.

Results

The best fitting models identified three groups. One showed a relatively benign, slowly progressing trajectory (Group 1), a second showed a moderate, intermediately progressing trajectory (Group 2), and a third showed a more severe, rapidly progressing trajectory (Group 3). Stable trajectory-group membership occurred relatively early in the disease course, 5 years after initial motor symptom. Predictors of intermediate and more severe trajectory-group membership varied across the single variable models and the multivariable model jointly considering UPDRS-III, H&Y and MMSE scores. In the multivariable model, membership in Group 2 (28.4% of patients), relative to Group 1 (50.5%), was associated with male sex, younger age-at-onset, fewer education-years, pesticide exposure, absence of reported head injury, and akinetic/rigid subtype at initial presentation. Membership in Group 3 (21.3%), relative to Group 1, was associated with older age-at-onset, fewer education-years, pesticide exposure, and the absence of a tremor-predominant subtype at initial presentation. Persistent freezing, persistent falls, and cognitive impairment occurred earliest and more frequently in Group 3, later and less frequently in Group 2, and latest and least frequently in Group 1. Furthermore, autonomic complications, dysphagia, and psychosis occurred more frequently in Groups 2 and 3 than in Group 1.

Conclusion

Modeling disease course using multiple objective assessments over an extended follow-up duration identified groups that more accurately reflect differences in PD course, prognosis, and outcomes than assessing single parameters over shorter intervals.

Dementia Risk Prediction in a Longitudinal Geriatric Parkinson's Disease Cohort: Evaluation and Application of the Montreal Parkinson Risk of Dementia Scale

Background

Parkinson's disease (PD) increases risk for dementia and cascading adverse outcomes. The eight-item Montreal Parkinson Risk of Dementia Scale (MoPaRDS) is a rapid, in-office dementia screening tool. We examine predictive validity and other characteristics of the MoPaRDS in a geriatric PD cohort by testing a series of alternative versions and modelling risk score change trajectories.

Methods

Participants were 48 initially non-demented PD patients (Mage = 71.6 years, range = 65-84) from a three-year, three-wave prospective Canadian cohort study. A dementia diagnosis at Wave 3 was used to stratify two baseline groups: PD with Incipient Dementia (PDID) and PD with No Dementia (PDND). We aimed to predict dementia three years prior to diagnosis using baseline data for eight indicators that harmonized with the original report, plus education.

Results

Three MoPaRDS items (age, orthostatic hypotension, mild cognitive impairment [MCI]) discriminated the groups both independently and as a composite three-item scale (area under the curve [AUC] = 0.88). The eight-item MoPaRDS reliably discriminated PDID from PDND (AUC = 0.81). Education did not improve predictive validity (AUC = 0.77). Performance of the eight-item MoPaRDS varied across sex (AUCfemales = 0.91; AUCmales = 0.74), whereas the three-item configuration did not (AUCfemales = 0.88; AUCmales = 0.91). Risk scores of both configurations increased over time.

Conclusions

We report new data on the application of the MoPaRDS as a dementia prediction tool for a geriatric PD cohort. Results support the viability of the full MoPaRDS, and indicate that an empirically determined brief version is a promising complement.

Influence of cognitive reserve on cognitive and motor function in α-synucleinopathies: A systematic review protocol

Cognitive reserve has been used to justify neuropathologically unexplainable mismatches in Alzheimer's disease outcomes. Recent evidence has suggested this effect may be replicable across other conditions. However, it is still unclear whether cognitive reserve applies to α-synucleinopathies or to motor outcomes, or if medication confounds effects. This review protocol follows PRISMA-P guidelines and aims to investigate whether cognitive reserve can predict both cognitive and motor outcomes for α-synucleinopathy patients. MEDLINE (via PubMed), Scopus, psycINFO (via Ovid), CINAHL (via EBSCO), and Web of Science have been searched. Cross-sectional, cohort, case-control, and longitudinal studies investigating the association between cognitive reserve and cognitive and/or motor outcomes for Parkinson's disease, dementia with Lewy bodies, or multiple system atrophy will be included. Reviewers will independently perform screening, while also extracting data, assessing the risk of bias (using a version of the Quality in Prognostic Studies tool), and rating evidence quality (using GRADE). If possible, random-effects meta-analyses will be conducted for each unique outcome variable and α-synucleinopathy; otherwise, a narrative synthesis will be performed. Depending on the number of studies, exploratory analyses may involve meta-regression to assess potential confounding effects. Understanding the broader protective effect of cognitive reserve has significant implications for preventive interventions in the wider population.

Local striatal volume and motor reserve in drug-naïve Parkinson's disease

Motor reserve (MR) may explain why individuals with similar pathological changes show marked differences in motor deficits in Parkinson's disease (PD). In this study, we investigated whether estimated individual MR was linked to local striatal volume (LSV) in PD. We analyzed data obtained from 333 patients with drug naïve PD who underwent dopamine transporter scans and high-resolution 3-tesla T1-weighted structural magnetic resonance images. Using a residual model, we estimated individual MRs on the basis of initial UPDRS-III score and striatal dopamine depletion. We performed a correlation analysis between MR estimates and LSV. Furthermore, we assessed the effect of LSV, which is correlated with MR estimates, on the longitudinal increase in the levodopa-equivalent dose (LED) during the 4-year follow-up period using a linear mixed model. After controlling for intracranial volume, there was a significant positive correlation between LSV and MR estimates in the bilateral caudate, anterior putamen, and ventro-posterior putamen. The linear mixed model showed that the large local volume of anterior and ventro-posterior putamen was associated with the low requirement of LED initially and accelerated LED increment thereafter. The present study demonstrated that LSV is crucial to MR in early-stage PD, suggesting LSV as a neural correlate of MR in PD.

Potential Link Between Cognition and Motor Reserve in Patients With Parkinson's Disease

Objective

To investigate whether there is a link between cognitive function and motor reserve (i.e., individual capacity to cope with nigrostriatal dopamine depletion) in patients with newly diagnosed Parkinson's disease (PD).

Methods

A total of 163 patients with drug-naïve PD who underwent 18F-FP-CIT PET, brain MRI, and a detailed neuropsychological test were enrolled. We estimated individual motor reserve based on initial motor deficits and striatal dopamine depletion using a residual model. We performed correlation analyses between motor reserve estimates and cognitive composite scores. Diffusion connectometry analysis was performed to map the white matter fiber tracts, of which fractional anisotropy (FA) values were well correlated with motor reserve estimates. Additionally, Cox regression analysis was used to assess the effect of initial motor reserve on the risk of dementia conversion.

Results

The motor reserve estimate was positively correlated with the composite score of the verbal memory function domain (γ = 0.246) and with the years of education (γ = 0.251). Connectometry analysis showed that FA values in the left fornix were positively correlated with the motor reserve estimate, while no fiber tracts were negatively correlated with the motor reserve estimate. Cox regression analysis demonstrated that higher motor reserve estimates tended to be associated with a lower risk of dementia conversion (hazard ratio, 0.781; 95% confidence interval, 0.576-1.058).

Conclusion

The present study demonstrated that the motor reserve estimate was well correlated with verbal memory function and with white matter integrity in the left fornix, suggesting a possible link between cognition and motor reserve in patients with PD.

Identifying the white matter structural network of motor reserve in early Parkinson's disease

INTRODUCTION

Motor reserve refers to the individual capacity to cope with nigrostriatal dopamine depletion in Parkinson's disease (PD). This study aimed to explore the white matter structural network associated with motor reserve in patients with newly diagnosed PD.

METHODS

A total of 238 patients with early-stage drug-naïve PD who underwent ¹⁸F-FP-CIT PET and brain MRI scans at initial assessment were enrolled. We estimated individual motor reserve based on the Unified Parkinson's Disease Rating Scale Part III (UPDRS-III) scores and dopamine transporter availability in the posterior putamen using a residual model. Then, we performed threshold-free network-based statistics (TFNBS) analysis to identify the structural brain network associated with the estimated motor reserve. We also assessed the effect of the network connectivity strength on the longitudinal increase in levodopa-equivalent dose (LED).

RESULTS

The mean age at PD symptom onset was 69.10 ± 9.03 years and the mean UPDRS-III score at the time of PD diagnosis was 22.44 ± 9.72. TFNBS analysis identified a motor reserve-associated structural network whose nodes were mainly in the frontal region and cerebellum. Higher network strength (i.e., greater motor reserve) was associated with a slower longitudinal increase in LED during a 3-year follow-up period.

CONCLUSION

The structural brain network is associated with motor reserve in patients with PD. Connectivity strength within the identified network indicates the individual's capacity to tolerate PD-related pathologies, which is maintained with disease progression and affects the long-term motor prognosis of PD.

Cognitive reserve: a multidimensional protective factor in Parkinson's disease related cognitive impairment

We explored the association between cognitive reserve (CR) and Parkinson' s disease (PD) related cognitive deterioration.Forty PD patients and 12 matched healthy controls (HC) were enrolled. The PD group was balanced for the presence/absence of cognitive impairment. All participants underwent MOCA. CR was measured by the Brief Intelligence Test, and a new comprehensive tool, named Cognitive Reserve Test (CoRe-T), including sections on leisure activities and creativity.Participants with higher CR obtained a better MOCA score irrespective of the group they belonged to. At the same time, irrespective of the CR level, the performance of the HC group was always better in comparison to the PD group. Within the PD group, a higher frequency of leisure activities was associated to be cognitively unimpaired, independently by the severity of motor symptoms and age.CR could help to cope with PD-related cognitive decline. Its multidimensional nature could have important applications in prevention and rehabilitation interventions.

Premorbid Educational Attainment and Long-Term Motor Prognosis in Parkinson's Disease

BACKGROUND

Premorbid educational attainment is a well-known proxy of reserve, not only with regard to cognition, but also to motor symptoms.

OBJECTIVE

In the present study, we investigated the relationship between educational attainment and long-term motor prognosis in patients with Parkinson's disease (PD).

METHODS

We analyzed 466 patients with de novo PD without dementia who underwent dopamine transporter (DAT) scans and were followed up more than 2 years. Patients were divided into three groups: low education (years-of-education ≤6, n = 125), intermediate education (6 <years-of-education < 12, n = 108), and high education (years-of-education ≥12, n = 233). The effects of educational attainment on the development of levodopa-induced dyskinesia (LID), wearing-off, and freezing-of-gait, and longitudinal increase in levodopa-equivalent doses (LEDs) were assessed.

RESULTS

Multiple regression analysis showed that higher education was associated with milder parkinsonian symptoms after adjusting for DAT availability in the posterior putamen. Survival analysis showed that the rate of LID was significantly lower in the high education group than in the low education group (HR = 0.565, p = 0.010). A linear mixed model showed that the high education group had lower LED than the low education group until a period of 30 months; however, this difference in LED was not observed thereafter.

CONCLUSION

The present study demonstrated that premorbid educational attainment has protective effects on the development of LID in patients with PD and has sparing effects on LED during the early treatment period. These results suggest that high educational attainment has a beneficial effect on motor outcomes in patients with PD.

Glucocerebrosidase Mutations and Motor Reserve in Parkinson's Disease

BACKGROUND

The concept of motor reserve explains the individual differences in motor deficits despite similar degrees of nigrostriatal dopamine depletion in Parkinson's disease (PD).

OBJECTIVE

To investigate glucocerebrosidase (GBA) variants as potential determinants of motor reserve for exploratory purposes.

METHODS

A total of 408 patients with drug-naïve PD were enrolled from the Parkinson's Progression Markers Initiative cohort database. All patients underwent SPECT dopamine transporter (DAT) scans and had results for Sanger sequencing of GBA. Parkinsonian motor deficits were assessed using the Movement Disorders Society Unified Parkinson's Disease Rating Scale Part III (MDS-UPDRS-III). We compared MDS-UPDRS-III scores while adjusting for DAT availability in the putamen (i.e., motor reserve) between the PD groups according to the presence of GBA mutations.

RESULTS

Fifty-four (13.2%) patients carried GBA mutations. PD patients with GBA mutations were younger than those without mutations. There were no significant differences in sex, disease duration, years of education, and striatal DAT availability between the PD groups. PD patients with GBA mutations had higher MDS-UPDRS-III scores for the less affected side than those without mutations, despite similar levels of DAT availability in the contralateral putamen. The MDS-UPDRS-III sub-scores of the more affected side did not differ between the two PD groups.

CONCLUSION

The results of this study demonstrated the detrimental effect of GBA variants on individual capacity to cope with PD-related pathologies, with different impacts depending on the motor laterality.

Impact of cognitive reserve on dance intervention-induced changes in brain plasticity

Dance is a complex sensorimotor activity with positive effects on physical fitness, cognition, and brain plasticity in the aging population. We explored whether individual levels of cognitive reserve (CR) proxied by education moderate dance intervention (DI)-induced plasticity assessed by resting-state functional connectivity (rs-FC) changes of the sensorimotor network (SMN), and between the dorsal attention network (DAN) and anterior default mode network (aDMN). Our cohort consisted of 99 subjects, randomly assigned to either a DI group who underwent a 6-month intervention (n = 49, M_age = 69.02 ± 5.40) or a control group (n = 50, M_age = 69.37 ± 6.10). Moderation analyses revealed that CR moderated DI-induced increase of the SMN rs-FC with significant changes observed in participants with ≥ 15 years of education (b = 0.05, t(62) = 3.17, p = 0.002). Only DI alone was a significant predictor of the DAN-aDMN crosstalk change (b = 0.06, t(64) = 2.16, p = 0.035). The rs-FC increase in the SMN was correlated with an improved physical fitness measure, and changes in the DAN-aDMN connectivity were linked to better performance on figural fluency. Consistent with the passive CR hypothesis, we observed that CR correlated only with baseline behavioral scores, not their change.

Possible Link between SARS-CoV-2 Infection and Parkinson's Disease: The Role of Toll-Like Receptor 4

Parkinson's disease (PD) is the most common neurodegenerative motor disorder characterized by selective degeneration of dopaminergic neurons in the substantia nigra pars compacta (SNpc) of the midbrain, depletion of dopamine (DA), and impaired nigrostriatal pathway. The pathological hallmark of PD includes the aggregation and accumulation α-synuclein (α-SYN). Although the precise mechanisms underlying the pathogenesis of PD are still unknown, the activation of toll-like receptors (TLRs), mainly TLR4 and subsequent neuroinflammatory immune response, seem to play a significant role. Mounting evidence suggests that viral infection can concur with the precipitation of PD or parkinsonism. The recently identified coronavirus named severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is the causative agent of ongoing pandemic coronavirus disease 2019 (COVID-19), responsible for 160 million cases that led to the death of more than three million individuals worldwide. Studies have reported that many patients with COVID-19 display several neurological manifestations, including acute cerebrovascular diseases, conscious disturbance, and typical motor and non-motor symptoms accompanying PD. In this review, the neurotropic potential of SARS-CoV-2 and its possible involvement in the pathogenesis of PD are discussed. Specifically, the involvement of the TLR4 signaling pathway in mediating the virus entry, as well as the massive immune and inflammatory response in COVID-19 patients is explored. The binding of SARS-CoV-2 spike (S) protein to TLR4 and the possible interaction between SARS-CoV-2 and α-SYN as contributing factors to neuronal death are also considered.

Prodromal Parkinson disease subtypes - key to understanding heterogeneity

In Parkinson disease (PD), pathological processes and neurodegeneration begin long before the cardinal motor symptoms develop and enable clinical diagnosis. In this prodromal phase, risk and prodromal markers can be used to identify individuals who are likely to develop PD, as in the recently updated International Parkinson and Movement Disorders Society research criteria for prodromal PD. However, increasing evidence suggests that clinical and prodromal PD are heterogeneous, and can be classified into subtypes with different clinical manifestations, pathomechanisms and patterns of spatial and temporal progression in the CNS and PNS. Genetic, pathological and imaging markers, as well as motor and non-motor symptoms, might define prodromal subtypes of PD. Moreover, concomitant pathology or other factors, including amyloid-β and tau pathology, age and environmental factors, can cause variability in prodromal PD. Patients with REM sleep behaviour disorder (RBD) exhibit distinct patterns of α-synuclein pathology propagation and might indicate a body-first subtype rather than a brain-first subtype. Identification of prodromal PD subtypes and a full understanding of variability at this stage of the disease is crucial for early and accurate diagnosis and for targeting of neuroprotective interventions to ensure efficacy.

Rhythm and groove as cognitive mechanisms of dance intervention in Parkinson's disease

Parkinson's disease (PD) is associated with a loss of internal cueing systems, affecting rhythmic motor tasks such as walking and speech production. Music and dance encourage spontaneous rhythmic coupling between sensory and motor systems; this has inspired the development of dance programs for PD. Here we assessed the therapeutic outcome and some underlying cognitive mechanisms of dance classes for PD, as measured by neuropsychological assessments of disease severity as well as quantitative assessments of rhythmic ability and sensorimotor experience. We assessed prior music and dance experience, beat perception (Beat Alignment Test), sensorimotor coupling (tapping to high- and low-groove songs), and disease severity (Unified Parkinson's Disease Rating Scale in PD individuals) before and after four months of weekly dance classes. PD individuals performed better on UPDRS after four months of weekly dance classes, suggesting efficacy of dance intervention. Greater post-intervention improvements in UPDRS were associated with the presence of prior dance experience and with more accurate sensorimotor coupling. Prior dance experience was additionally associated with enhanced sensorimotor coupling during tapping to both high-groove and low-groove songs. These results show that dance classes for PD improve both qualitative and quantitative assessments of disease symptoms. The association between these improvements and dance experience suggests that rhythmic motor training, a mechanism underlying dance training, impacts improvements in parkinsonian symptoms following a dance intervention.

Baseline cognitive profile is closely associated with long-term motor prognosis in newly diagnosed Parkinson's disease

OBJECTIVES

To investigate the association between cognitive function at baseline and the progression of motor disability in Parkinson's disease (PD).

METHODS

We consecutively enrolled 257 drug-naïve patients with early-stage PD (follow-up > 2 years) who underwent a detailed neuropsychological test at initial assessment. Factor analysis was conducted to yield four cognitive function factors and composite scores thereof: Factor 1 (visual memory/visuospatial), Factor 2 (verbal memory), Factor 3 (frontal/executive), and Factor 4 (attention/working memory/language). The global cognitive composite score of each patient was calculated based on these factors. Subsequently, we assessed the effect of baseline cognitive function on long-term motor outcomes, namely levodopa-induced dyskinesia (LID), wearing-off, freezing of gait (FOG), and rate of longitudinal increases in levodopa-equivalent dose (LED).

RESULTS

Cox regression analysis demonstrated that higher Factor 3 (frontal/executive) composite scores (i.e., better cognitive performance) were associated with early development of LID [hazard ratio (HR), 1.507; p = 0.003], whereas higher Factor 1 (visual memory/visuospatial) composite scores (i.e., better cognitive performance) were associated with a lower risk for FOG (HR 0.683; p = 0.017). We noted that higher global cognitive composite scores were associated with a lower risk for developing FOG (HR 0.455; p = 0.045). The linear mixed model demonstrated that higher global cognitive composite scores and better cognitive performance in visual memory/visuospatial function were associated with slower longitudinal increases in LED.

CONCLUSIONS

These findings suggest that baseline cognitive profiles have prognostic implications on several motor aspects in patients with PD.

Statistically Defined Parkinson's Disease Executive and Memory Cognitive Phenotypes: Demographic, Behavioral, and Structural Neuroimaging Comparisons

BACKGROUND

Some individuals with Parkinson's disease (PD) experience working memory and inhibitory difficulties, others learning and memory difficulties, while some only minimal to no cognitive deficits for many years.

OBJECTIVE

To statistically derive PD executive and memory phenotypes, and compare PD phenotypes on disease and demographic variables, vascular risk factors, and specific neuroimaging variables with known associations to executive and memory function relative to non-PD peers.

METHODS

Non-demented individuals with PD (n = 116) and non-PD peers (n = 62) were recruited to complete neuropsychology measures, blood draw, and structural magnetic resonance imaging. Tests representing the cognitive domains of interest (4 executive function, 3 memory) were included in a k-means cluster analysis comprised of the PD participants. Resulting clusters were compared demographic and disease-related variables, vascular risk markers, gray/white regions of interest, and white matter connectivity between known regions involved in executive and memory functions (dorsolateral prefrontal cortices to caudate nuclei; entorhinal cortices to hippocampi).

RESULTS

Clusters showed: 1) PD Executive, n = 25; 2) PD Memory, n = 35; 3) PD Cognitively Well; n = 56. Even after disease variable corrections, PD Executive had less subcortical gray matter, white matter, and fewer bilateral dorsolateral-prefrontal cortex to caudate nucleus connections; PD Memory showed bilaterally reduced entorhinal-hippocampal connections. PD Cognitively Well showed only reduced putamen volume and right entorhinal cortex to hippocampi connections relative to non-PD peers. Groups did not statistically differ on cortical integrity measures or cerebrovascular disease markers.

CONCLUSION

PD cognitive phenotypes showed different structural gray and white matter patterns. We discuss data relative to phenotype demographics, cognitive patterns, and structural brain profiles.

Cognitive reserve is associated with altered clinical expression in amyotrophic lateral sclerosis

Objective: Long-term life experiences, such as education, occupational attainment, leisure activities, and bilingualism, have been considered proxies of cognitive reserve (CR). In neurodegenerative disease, CR is considered as a modulator of a more favorable cognitive trajectory and motor functions. Our study investigated the role of CR on cognitive and motor involvement in a large cohort of incident patients with amyotrophic lateral sclerosis (ALS). Methods: Cognition assessment and clinical and demographic information were obtained in 101 incident ALS patients. CR was measured based on years of education, occupational attainment, amount of leisure activities, and bilingualism. Correlation and regression analyses were performed to test the association between CR and the clinical expression of ALS. Results: We found that all proxies of CR were positively associated with executive functions, verbal fluency, and memory domains. Motor impairment was inversely related to educational level and occupational attainment. Regression analysis documented the association between CR and cognitive performances in all patients and the predictive role of CR in modulating motor functional disability in patients with bulbar-onset. Conclusion: Our findings showed that CR mediates the extent of cognitive decline and that of functional bulbar impairment, suggesting that the concept of reserve applied to ALS should encompass cognitive and motor domains.

Cerebello-basal ganglia connectivity fingerprints related to motor/cognitive performance in Parkinson's disease

INTRODUCTION

The role of the cerebellum in Parkinson's disease (PD) has attracted increasing attention; however, the role of functional connectivity (FC) between the basal ganglia and particular cerebellar subregions remains to be elucidated. We aimed to clarify the FC and its contribution to motor and cognitive performances in patients with PD.

METHODS

We included 99 patients with PD and 99 age- and sex-matched healthy controls in this study. We created a cerebellar functional parcellation by performing cerebellum-only independent component analysis. Using the functional parcellation map, we performed seed-based connectivity analysis using each region as a seed and extracted the mean correlation coefficients within the thalamus and basal ganglia, including the caudate, pallidum, putamen and subthalamic nucleus. We examined the group differences and correlations with the motor and general cognitive scores. In addition, we conducted a mediation analysis to clarify the relationship among FC, motor severity, and cognition.

RESULTS

The PD group showed decreased FC between a wide range of cerebellar subregions and the basal ganglia. Motor severity was correlated with FC between the subthalamic nucleus and posterior Crus I/II, and general cognitive performance scores correlated with FC between the caudate nucleus and medial-posterior part of the Crus I/II (p < 0.05, corrected for multiple comparisons). The cerebello-caudate network had a direct effect on cognitive performance (p = 9.0 × 10^-3), although partially mediated by motor performance (p = 8.2 × 10^-3).

CONCLUSION

FC between cerebellar Crus I/II and divergent basal ganglia related to motor and cognitive performance in PD.

Emerging Concepts of Motor Reserve in Parkinson's Disease

The concept of cognitive reserve (CR) in Alzheimer's disease (AD) explains the differences between individuals in their susceptibility to AD-related pathologies. An enhanced CR may lead to less cognitive deficits despite severe pathological lesions. Parkinson's disease (PD) is also a common neurodegenerative disease and is mainly characterized by motor dysfunction related to striatal dopaminergic depletion. The degree of motor deficits in PD is closely correlated to the degree of dopamine depletion; however, significant individual variations still exist. Therefore, we hypothesized that the presence of motor reserve (MR) in PD explains the individual differences in motor deficits despite similar levels of striatal dopamine depletion. Since 2015, we have performed a series of studies investigating MR in de novo patients with PD using the data of initial clinical presentation and dopamine transporter PET scan. In this review, we summarized the results of these published studies. In particular, some premorbid experiences (i.e., physical activity and education) and modifiable factors (i.e., body mass index and white matter hyperintensity on brain image studies) could modulate an individual's capacity to tolerate PD pathology, which can be maintained throughout disease progression.

Longitudinal Monitoring of Parkinson's Disease in Different Ethnic Cohorts: The DodoNA and LONG-PD Study

Background: Different factors influence severity, progression, and outcomes in Parkinson's disease (PD). Lack of standardized clinical assessment limits comparison of outcomes and availability of well-characterized cohorts for collaborative studies. Methods: Structured clinical documentation support (SCDS) was developed within the DNA Predictions to Improve Neurological Health (DodoNA) project to standardize clinical assessment and identify molecular predictors of disease progression. The Longitudinal Clinical and Genetic Study of Parkinson's Disease (LONG-PD) was launched within the Genetic Epidemiology of Parkinson's disease (GEoPD) consortium using a Research Electronic Data Capture (REDCap) format mirroring the DodoNA SCDS. Demographics, education, exposures, age at onset (AAO), Unified Parkinson's Disease Rating Scale (UPDRS) parts I-VI or Movement Disorders Society (MDS)-UPDRS, Montreal Cognitive Assessment (MoCA)/Short Test of Mental Status (STMS)/Mini Mental State Examination (MMSE), Geriatric Depression Scale (GDS), Epworth Sleepiness Scale (ESS), dopaminergic therapy, family history, nursing home placement, death and blood samples were collected. DodoNA participants (396) with 6 years of follow-up and 346 LONG-PD participants with up to 3 years of follow-up were analyzed using group-based trajectory modeling (GBTM) focused on: AAO, education, family history, MMSE/MoCA/STMS, UPDRS II-II, UPDRS-III tremor and bradykinesia sub-scores, Hoehn and Yahr staging (H&Y) stage, disease subtype, dopaminergic therapy, and presence of autonomic symptoms. The analysis was performed with either cohort as the training/test set. Results: Patients are classified into slowly and rapidly progressing courses by AAO, MMSE score, H &Y stage, UPDRS-III tremor and bradykinesia sub-scores relatively early in the disease course. Late AAO and male sex assigned patients to the rapidly progressing group, whereas tremor to the slower progressing group. Classification is independent of which cohort serves as the training set. Frequencies of disease-causing variants in LRRK2 and GBA were 1.89 and 2.96%, respectively. Conclusions: Standardized clinical assessment provides accurate phenotypic characterization in pragmatic clinical settings. Trajectory analysis identified two different trajectories of disease progression and determinants of classification. Accurate phenotypic characterization is essential in interpreting genomic information that is generated within consortia, such as the GEoPD, formed to understand the genetic epidemiology of PD. Furthermore, the LONGPD study protocol has served as the prototype for collecting standardized phenotypic information at GEoPD sites. With genomic analysis, this will elucidate disease etiology and lead to targeted therapies that can improve disease outcomes.

Education Moderates the Association of Probable REM Sleep Behavior Disorder With Cognitive and Motor Impairments in Community-Dwelling Older People

Objectives: To investigate the relationship between probable rapid eye movement (REM) sleep behavior disorder (pRBD) and cognitive/motor impairments in a community-dwelling population and explore the moderating effects of education. Methods: In this cross-sectional study of the Beijing Longitudinal Study of Aging II (BLSA II), 4,477 subjects (≥55 years) fulfilled the inclusion criteria. pRBD was determined by the RBD Questionnaire-Hong Kong (RBDQ-HK). Mini-Mental State Examination (MMSE) and Montreal Cognitive Assessment (MoCA) were used to test the global cognitive performance. Walking speed was used to measure motor function. Logistic regression was performed to assess the relationship between pRBD and cognitive/motor impairments and the moderating effects of education. Results: There were 147 participants (3.3%) with pRBD. Participants with pRBD showed increased risks for cognitive impairment [odds ratio (OR) = 1.88, 95% CI 1.24-2.85, p = 0.003], decreased gait speed (OR = 1.43, 95% CI 1.02-2.01, p = 0.03), but not for mild cognitive impairment (MCI) (measured by MoCA: OR = 1.01, 95% CI 0.68-1.50, p = 0.95; measured by MMSE: OR = 0.90, 95% CI 0.59-1.37, p = 0.62). Education modified the effect of pRBD on MCI (measured by MoCA: p < 0.001; measured by MMSE: p = 0.061) and gait speed (p = 0.008). Conclusions: Our findings suggest that pRBD increases the risk of cognitive/motor impairments for a community-dwelling older population, and education could alleviate the negative effects. These findings implicate that education may have beneficial effects on delaying the onset of cognitive/motor decline in pRBD subjects.

Initial motor reserve and long-term prognosis in Parkinson's disease

There are individual differences in motor deficits, despite a similar degree of dopamine neuronal loss in Parkinson's disease (PD), called motor reserve (MR). Factors enhancing MR have been documented previously, but the influence of initial MR on the long-term prognosis remains unclear. In this longitudinal study, we enrolled 205 patients with de novo PD to estimate individual MR based on initial motor deficits and striatal dopamine depletion using the residual-based approach. We assessed the risk of developing levodopa-induced dyskinesia (LID) or freezing of gait (FOG) and longitudinal increases in levodopa-equivalent dose (LED) according to MR estimates using the Cox regression model and linear mixed model, respectively. Throughout the follow-up period (≥3 years), greater MR estimates were associated with a lower risk for LID and FOG. In addition, patients with high MR received lower LED than those with low MR. These findings suggest that the initial MR, that is, individual's capacity to cope with PD-related pathologies, can be maintained with disease progression and can modulate the risk for LID or FOG.

Identifying the Functional Brain Network of Motor Reserve in Early Parkinson's Disease

BACKGROUND

The severity of motor symptoms in Parkinson's disease (PD) does not always correlate with the degree of nigral dopaminergic neuronal loss. Individuals with greater motor reserve may have milder motor signs than their striatal dopamine loss. In this study, we explored the functional brain network associated with motor reserve in early-stage PD.

METHODS

We analyzed 134 patients with de novo PD who underwent dopamine transporter scans and resting-state functional magnetic resonance imaging. We estimated individual motor reserve based on initial motor deficits and striatal dopamine depletion using a residual model. We applied network-based statistic analysis to identify the functional brain network associated with the measure of motor reserve (ie, motor reserve network). We also assessed the effect of motor reserve network connectivity strength on the longitudinal increase in levodopa-equivalent dose during the 2-year follow-up period.

RESULTS

Network-based statistic analysis identified the motor reserve network composed of the basal ganglia, inferior frontal cortex, insula, and cerebellar vermis at a primary threshold of P value 0.001. Patients with an increased degree of functional connectivity within the motor reserve network had greater motor reserve. There was a significant interaction between the motor reserve network strength and time in the linear mixed model, indicating that higher motor reserve network strength was associated with slower longitudinal increase in levodopa-equivalent dose.

CONCLUSIONS

The present study revealed the functional brain network associated with motor reserve in patients with early-stage PD. Functional connections within the motor reserve network are associated with the individual's capacity to cope with PD-related pathologies. © 2020 International Parkinson and Movement Disorder Society.

Association of leucine-rich repeat kinase 2 gene rs10878307 polymorphism and Parkinson's disease risk in South India-A meta-analysis and molecular dynamics simulation

Communicated by Ramaswamy H. Sarma.