Depression and the subsequent risk of Parkinson's disease in the NIH-AARP Diet and Health Study

Depressive Symptoms and the Subsequent Risk of Parkinson's Disease: A Nationwide Cohort Study

OBJECTIVE

Only a few studies have focused on depressive symptoms and Parkinson's disease (PD) risk. As a time lag exists from the onset of depressive symptoms to the diagnosis of depression, elucidating the association between depressive symptoms and PD development might be helpful for the early prediction of PD. We investigate the association between depressive symptoms and subsequent PD risk using nationwide population-based cohort database.

DESIGN AND SETTING

Cohort study using the Korean National Health Insurance Service data between 2007 and 2017, with longitudinal follow-up until 2019.

PARTICIPANTS

A total of 98,296 elderly people responded to a self-reported questionnaire from the National Health Screening Program on depressive symptoms.

MEASUREMENTS

The association between depressive symptoms such as 1) decreased activity or motivation, 2) worthlessness, and 3) hopelessness and PD risk was analyzed.

RESULTS

During median 5.06-year follow-up, 839 PD cases occurred: 230 in individuals with depressive symptoms and 609 in those without symptoms. Results showed an increased risk of PD development in those with depressive symptoms (HR = 1.47, 95% CI, 1.26-1.71), with dose-response association between the number of depressive symptoms and PD risk. Even in those already diagnosed with depression, combined depressive symptoms were linked to a higher risk compared to those without symptoms (with symptoms, HR = 2.71, 95% CI, 2.00-3.68; without symptoms, HR = 1.84, 95% CI, 1.43-2.36).

CONCLUSION

Individuals with depressive symptoms were at an increased risk of developing PD, and there was a dose-response association between the number of depressive symptoms and PD risk.

Different risks of early-onset and late-onset Parkinson disease in individuals with mental illness

We aimed to investigate the association of various mental illnesses, including depression, bipolar disorder, schizophrenia, insomnia, and anxiety, with the risk of early-onset Parkinson's disease (EOPD) (age <50 years) and compare it with that of late-onset PD (LOPD) (age ≥50 years). This nationwide cohort study enrolled 9,920,522 people who underwent a national health screening examination in 2009, and followed up until 31 December 2018. There was a significantly increased risk of EOPD and LOPD in individuals with mental illness, and EOPD showed a stronger association than LOPD (EOPD, hazard ratio (HR) = 3.11, 95% CI: 2.61‒3.72; LOPD, HR = 1.70, 95% CI: 1.66‒1.74; p for interaction <0.0001). Our results suggest that people with mental illnesses aged < 50 years are at a higher risk of PD than those aged ≥50 years. Future studies are warranted to elucidate the pathomechanism of EOPD in relation to mental illness.

Could the Urease of the Gut Bacterium Proteus mirabilis Play a Role in the Altered Gut-Brain Talk Associated with Parkinson's Disease?

Intestinal dysbiosis seems to play a role in neurodegenerative pathologies. Parkinson's disease (PD) patients have an altered gut microbiota. Moreover, mice treated orally with the gut microbe Proteus mirabilis developed Parkinson's-like symptoms. Here, the possible involvement of P. mirabilis urease (PMU) and its B subunit (PmUreβ) in the pathogenesis of PD was assessed. Purified proteins were given to mice intraperitoneally (20 μg/animal/day) for one week. Behavioral tests were conducted, and brain homogenates of the treated animals were subjected to immunoassays. After treatment with PMU, the levels of TNF-α and IL-1β were measured in Caco2 cells and cellular permeability was assayed in Hek 293. The proteins were incubated in vitro with α-synuclein and examined via transmission electron microscopy. Our results showed that PMU treatment induced depressive-like behavior in mice. No motor deficits were observed. The brain homogenates had an increased content of caspase-9, while the levels of α-synuclein and tyrosine hydroxylase decreased. PMU increased the pro-inflammatory cytokines and altered the cellular permeability in cultured cells. The urease, but not the PmUreβ, altered the morphology of α-synuclein aggregates in vitro, forming fragmented aggregates. We concluded that PMU promotes pro-inflammatory effects in cultured cells. In vivo, PMU induces neuroinflammation and a depressive-like phenotype compatible with the first stages of PD development.

Screening and Targeting Risk Factors for Prodromal Synucleinopathy: Taking Steps toward a Prescriptive Multi-modal Framework

As the prevalence of Parkinson's disease (PD) grows, so too does the population at-risk of developing PD, those in the so-called prodromal period. This period can span from those experiencing subtle motor deficits yet not meeting full diagnostic criteria or those with physiologic markers of disease alone. Several disease-modifying therapies have failed to show a neuroprotective effect. A common criticism is that neurodegeneration, even in the early motor stages, has advanced too far for neuro-restoration-based interventions to be effective. Therefore, identifying this early population is essential. Once identified, these patients could then potentially benefit from sweeping lifestyle modifications to alter their disease trajectory. Herein, we review the literature on risk factors for, and prodromal symptoms of, PD with an emphasis on ones which may be modifiable in the earliest possible stages. We propose a process for identifying this population and speculate on some strategies which may modulate disease trajectory. Ultimately, this proposal warrants prospective studies.

Depressive symptoms before and after Parkinson’s diagnosis—A longitudinal analysis

Background

Depression is common in Parkinson’s disease (PD). It is however unclear when and how depressive symptoms develop and progress in the course of PD development.

Objective

To assess how depressive symptoms evolve in PD, using repeated measures.

Methods

In 2994 older adults, ages 70–79 years, depressive symptoms were assessed 8 times over 11 years using the 10-item Center for Epidemiologic Studies Depression Scale (CESD-10). For each PD patient at each time point, we calculated the difference between CESD-10 score and its expected value estimated based on data from individuals without PD, and then realigned the time scale in reference to the year of PD diagnosis. We examined longitudinal changes in CESD-10 scores before and after PD diagnosis using a joint modeling approach to account for competing risks of non-participation and death.

Results

A total of 79 PD patients were identified at enrollment or during the follow-up, with repeatedly assessed depressive symptom data up to 9 years before and after PD diagnosis. We found a monotonic trend of increasing CESD-10 score in PD patients throughout the observational period (p = 0.002). The observed scores became higher than expected approximately 7 years before PD diagnosis and significantly different 1 year before PD diagnosis.

Conclusions

Increasing depressive symptomatology appears to precede PD diagnosis by a few years.

Depression in Patients with Parkinson's Disease: Current Understanding of its Neurobiology and Implications for Treatment

Depression is one of the most frequent and burdensome non-motor symptoms in Parkinson’s disease (PD), across all stages. Even when its severity is mild, PD depression has a great impact on quality of life for these patients and their caregivers. Accordingly, accurate diagnosis, supported by validated scales, identification of risk factors, and recognition of motor and non-motor symptoms comorbid to depression are critical to understanding the neurobiology of depression, which in turn determines the effectiveness of dopaminergic drugs, antidepressants and non-pharmacological interventions. Recent advances using in vivo functional and structural imaging demonstrate that PD depression is underpinned by dysfunction of limbic networks and monoaminergic systems, depending on the stage of PD and its associated symptoms, including apathy, anxiety, rapid eye movement sleep behavior disorder (RBD), cognitive impairment and dementia. In particular, the evolution of serotonergic, noradrenergic, and dopaminergic dysfunction and abnormalities of limbic circuits across time, involving the anterior cingulate and orbitofrontal cortices, amygdala, thalamus and ventral striatum, help to delineate the variable expression of depression in patients with prodromal, early and advanced PD. Evidence is accumulating to support the use of dual serotonin and noradrenaline reuptake inhibitors (desipramine, nortriptyline, venlafaxine) in patients with PD and moderate to severe depression, while selective serotonin reuptake inhibitors, repetitive transcranial magnetic stimulation and cognitive behavioral therapy may also be considered. In all patients, recent findings advocate that optimization of dopamine replacement therapy and evaluation of deep brain stimulation of the subthalamic nucleus to improve motor symptoms represents an important first step, in addition to physical activity. Overall, this review indicates that increasing understanding of neurobiological changes help to implement a roadmap of tailored interventions for patients with PD and depression, depending on the stage and comorbid symptoms underlying PD subtypes and their prognosis.

Prodromal depression and subsequent risk of developing Parkinson's disease: a systematic review with meta-analysis

Aim: Parkinson's disease (PD) is a progressive neurological disorder that predominately affects dopaminergic neurons. We believe that this pooling of data will help to better understand the prodromal nature of depression in PD. Materials & methods: We conducted this study in accordance with PRISMA guidelines 2020. Fifteen eligible articles were shortlisted for final analysis. Risk of bias assessment was also conducted Results: The random-effect model revealed that the risk of subsequent Parkinson's disease in patients with prodromal depression was twice as likely (OR, 2.04; 95% CI, 1.02-4.08) as compared with a healthy population. Conclusion: Our meta-analysis concluded that the subsequent risk of PD is significantly higher in patients with depression as compared with healthy individuals.

Dose-Response Association of Metformin with Parkinson's Disease Odds in Type 2 Diabetes Mellitus

Background. Studies have demonstrated that patients with diabetes mellitus who receive metformin have a lower risk of developing Parkinson’s disease (PD). However, studies have also suggested that metformin may increase the risk of PD. In this study, we investigated whether metformin use was associated with the risk of PD in type 2 diabetes mellitus (T2DM). Methods. In this population-based cross-sectional study, patients with T2DM diagnosed between 2001 and 2018 were enrolled. We categorized these patients as metformin users or nonusers. Participants below 50 years old were excluded. Two models were employed to evaluate the associations of metformin exposure and use intensity with PD after 3 and 5 years of follow-up. Results. Patients with T2DM who received <300 cumulative defined daily doses (cDDD) of metformin and those with metformin use intensity of <10 DDD/month had respective odds ratios (ORs) for PD of 0.88 (95% confidence interval [CI] = 0.83−0.94) and 0.87 (95% CI = 0.81−0.93) in a 3-year follow-up. In a 5-year follow-up, such patients had respective ORs for PD of 0.94 (95% CI = 0.90−0.98) and 0.93 (95% CI = 0.89−0.98). Patients with T2DM who received ≥300 cDDD of metformin or used metformin with intensity of ≥10 DDD/month experienced no neuroprotective effects after 3 or 5 years. Conclusions. Metformin was associated with PD odds in T2DM in a dose−response association manner. Patients who received low dosage and intensity of metformin use were associated with lower odds of PD, while higher dosage and intensity of metformin use had no neuroprotective effect.

Investigating the Convergent Mechanisms between Major Depressive Disorder and Parkinson's Disease

Major depressive disorder (MDD) affects more than cognition, having a temporal relationship with neuroinflammatory pathways of Parkinson's disease (PD). Although this association is supported by epidemiological and clinical studies, the underlying mechanisms are unclear. Microglia and astrocytes play crucial roles in the pathophysiology of both MDD and PD. In PD, these cells can be activated by misfolded forms of the protein α-synuclein to release cytokines that can interact with multiple different physiological processes to produce depressive symptoms, including monoamine transport and availability, the hypothalamus-pituitary axis, and neurogenesis. In MDD, glial cell activation can be induced by peripheral inflammatory agents that cross the blood-brain barrier and/or c-Fos signalling from neurons. The resulting neuroinflammation can cause neurodegeneration due to oxidative stress and glutamate excitotoxicity, contributing to PD pathology. Astrocytes are another major link due to their recognized role in the glymphatic clearance mechanism. Research suggesting that MDD causes astrocytic destruction or structural atrophy highlights the possibility that accumulation of α-synuclein in the brain is facilitated as the brain cannot adequately clear the protein aggregates. This review examines research into the overlapping pathophysiology of MDD and PD with particular focus on the roles of glial cells and neuroinflammation.

Low-frequency and rare coding variants of NUS1 contribute to susceptibility and phenotype of Parkinson's disease

NUS1 has been recently identified as a candidate gene for Parkinson's disease (PD). Few studies have examined the association of NUS1 variants with PD susceptibility and phenotypes. In the first cohort, whole-exome sequencing was performed to identify variants in NUS1 exon-coding and exon-intron regions in 1542 cases and 1625 controls. 13 variants were totally detected, of which 10 rare variants and 3 low-frequency variants. Burden analysis showed that rare NUS1 variants significantly enriched in PD (p=0.016). We also performed a meta-analysis based on previous and our studies to correlate NUS1 mutations with PD susceptibility. Integrating our previous cohort (3210 cases and 2807 controls) and the first cohort identified the significant association of rs539668656 with PD risk (odds ratio (OR) = 2.82, p = 0.016). The genotype-phenotype association analysis showed that patients carrying rare variants, or rs539668656 were significantly associated with earlier onset age, depression, emotional impairment and severe disease condition. Our results support the role of NUS1 rare variants and rs539668656 towards PD susceptibility and phenotype.

Lipocalin 2 as a link between ageing, risk factor conditions and age-related brain diseases

Chronic (neuro)inflammation plays an important role in many age-related central nervous system (CNS) diseases, including Alzheimer's disease, Parkinson's disease and vascular dementia. Inflammation also characterizes many conditions that form a risk factor for these CNS disorders, such as physical inactivity, obesity and cardiovascular disease. Lipocalin 2 (Lcn2) is an inflammatory protein shown to be involved in different age-related CNS diseases, as well as risk factor conditions thereof. Lcn2 expression is increased in the periphery and the brain in different age-related CNS diseases and also their risk factor conditions. Experimental studies indicate that Lcn2 contributes to various neuropathophysiological processes of age-related CNS diseases, including exacerbated neuroinflammation, cell death and iron dysregulation, which may negatively impact cognitive function. We hypothesize that increased Lcn2 levels as a result of age-related risk factor conditions may sensitize the brain and increase the risk to develop age-related CNS diseases. In this review we first provide a comprehensive overview of the known functions of Lcn2, and its effects in the CNS. Subsequently, this review explores Lcn2 as a potential (neuro)inflammatory link between different risk factor conditions and the development of age-related CNS disorders. Altogether, evidence convincingly indicates Lcn2 as a key constituent in ageing and age-related brain diseases.

Trend of recognizing depression symptoms and antidepressants use in newly diagnosed Parkinson's disease: Population-based study

OBJECTIVES

Although depression symptoms are common among patients with Parkinson's disease (PD), the medical literature still reports underrecognition of depression in patients with PD. Our main objective is to examine the trend of depression recognition during the first year of PD diagnosis using large population data.

METHODS

We conducted a population-based study of residents in Wales, using the Secure Anonymized Information Linkage (SAIL) Databank. We included newly diagnosed patients with PD aged 40 years or older with a first PD diagnosis between 2000 and 2015. Depression and antidepressants related data were extracted from SAIL. A series of multilevel logistic regressions were run to determine the factors affecting depression recognition. The results were presented using odds ratios (ORs) with 95% confidence intervals (CI).

RESULTS

The study included 6596 patients with PD. About 38% of patients had a recorded code of antidepressants, depression diagnosis, or both within the first year of PD diagnosis. There was a significant association of depression diagnosis, antidepressant use, or both with the year of PD diagnosis (OR 0.972, 95% CI 0.962-0.983). We also found that patients who used monoamine oxidase inhibitors (MAO-B inhibitors) were associated with a lower depression diagnosis, use antidepressants, or both, compared to those who did not use MAO-B inhibitors (OR 0.769, 95% CI 0.627-0.943).

CONCLUSION

There is a slight decrease in depression recognition in PD patients between 2000 and 2015, which could be due to an increase in depression recognition during the prodromal phase of PD.

Is Attention-Deficit/Hyperactivity Disorder a Risk Syndrome for Parkinson's Disease?

Recent epidemiological evidence indicates that diagnosis of attention-deficit/hyperactivity disorder (ADHD) is associated with increased risk for diseases of the basal ganglia and cerebellum, including Parkinson's disease (PD). The evidence reviewed here indicates that deficits in striatal dopamine are a shared component of the causal chains that produce these disorders. Neuropsychological studies of adult ADHD, prodromal PD, and early-stage PD reveal similar deficits in executive functions, memory, attention, and inhibition that are mediated by similar neural substrates. These and other findings are consistent with the possibility that ADHD may be part of the PD prodrome. The mechanisms that may mediate the association between PD and ADHD include neurotoxic effects of stimulants, other environmental exposures, and Lewy pathology. Understanding the nature of the association between PD and ADHD may provide insight into the etiology and pathogenesis of both disorders. The possible contribution of stimulants to this association may have important clinical and public health implications.

Premotor Parkinson's disease: Overview of clinical symptoms and current diagnostic methods

Parkinson's disease (PD) is characterized by typical motor symptoms. However, recent studies show several non-motor features that may precede the development of the motor symptoms of PD. The best known premotor symptoms include hyposmia, REM sleep behavior disorder (RBD), constipation, and depression; other symptoms are excessive daytime somnolence, orthostatic hypotension and symptomatic hypotension, erectile or urinary dysfunction, musculoskeletal symptoms, pain, and global cognitive deficit. In this review, we summarize currently available diagnostic methods for these symptoms. We also briefly summarize neuroimaging, polyneuropathy, peripheral markers, and cerebrospinal fluid biomarkers that may be used in the early diagnosis of PD.

Management of psychiatric disorders in Parkinson's disease : Neurotherapeutics - Movement Disorders Therapeutics

Affective disorders (depression and anxiety), psychosis, impulse control disorders, and apathy are common and sometimes disabling psychiatric conditions in Parkinson disease (PD). Psychiatric aspects of PD are associated with numerous adverse outcomes, yet in spite of this and their high frequency, there remains incomplete understanding of epidemiology, presentation, risk factors, neural substrate, and management strategies. Psychiatric features are typically co- or multimorbid, and there is great intra- and interindividual variability in presentation [1]. The neuropathophysiological changes that occur in PD, as well as the association between PD treatment and particular psychiatric disorders, suggest a neurobiological contribution to many psychiatric symptoms. There is evidence that psychiatric disorders in PD are still under-recognized and undertreated, and although psychotropic medication use is common, randomized controlled trials demonstrating efficacy and tolerability are largely lacking. Future research on neuropsychiatric complications in PD should be oriented toward determining modifiable correlates or risk factors, and most importantly, establishing efficacious and well-tolerated treatment strategies.

Cognitive and functional changes in prediagnostic phase of Parkinson disease: A population-based study

INTRODUCTION

Prodromal non-motor symptoms precede, often by decades, motor signs and diagnosis of Parkinson's disease. It is however still uncertain if cognitive changes belong to the spectrum of non-motor prodromal Parkinson's disease. Thanks to the very long-term follow-up of the PAQUID population-based cohort, we assessed trajectories of cognitive complaints and functioning over a 13-year period before the diagnosis of late onset Parkinson's disease.

METHODS

This study relies on a matched nested case-control sample selected from the cohort. Of the 3777 initial subjects of the cohort, 43 developed incident Parkinson's disease over the follow-up. The mean age at diagnosis was 78.0 (standard deviation = 5.8) years and 46.5% were men. These cases were matched to 86 elderly control subjects. Scores of different cognitive domains, daily function, and depressive symptoms were described throughout the follow-up using mixed-effects models.

RESULTS

No significant global cognitive decline preceded the diagnosis of late onset Parkinson's disease. However, psychomotor speed appeared significantly slower 2 years before the diagnosis and depressive symptoms 12 years before. Global score of instrumental activities of daily living became altered 2-3 years preceding the diagnosis of late onset Parkinson's disease, including the use of public transportation that was altered ten years before the diagnosis.

CONCLUSION

In late onset Parkinson's disease, while global cognitive functions seem preserved, psychomotor speed starts to decline 2 years before the diagnosis and activities of daily living are also impacted. Depressive symptoms appear very early in the prediagnosic phase.

Depression Comorbid With Stroke, Traumatic Brain Injury, Parkinson's Disease, and Multiple Sclerosis: Diagnosis and Treatment

Depression is common among patients with neurologic disorders, and it has long been considered more difficult to treat than depression in the general population. In this review, the authors consider challenges in the diagnosis and treatment of depression among patients with stroke, traumatic brain injury, Parkinson's disease, and multiple sclerosis. For each disorder, the authors discuss the epidemiology and time course of depression as well as review the physiologic and psychological etiologies of depression. In addition, for each disorder, they review screening tools and diagnostic considerations, including differential diagnosis; discuss etiological factors, both neurobiological and psychological; and assess evidence for various depression treatments, including pharmacologic, psychosocial, and neuromodulatory therapies. The evidence suggests that depression is common among patients with neurologic disorders and that it is crucial for general psychiatrists to provide treatment for this population.

Ages at Onset of Anxiety and Depressive Disorders in Parkinson's Disease

OBJECTIVE

Parkinson's disease (PD) is a quintessential neuropsychiatric condition in which anxiety and depressive symptoms are common and may precede motor manifestations. The authors explored the ages at onset of anxiety and depressive disorders among patients with PD evaluated by psychiatrists at a deep brain stimulation center.

METHODS

Psychiatric diagnoses and ages at onset were collected via clinical interviews. The ages at PD diagnosis were ascertained by chart review. Onset ages for anxiety and depressive disorders (overall and for specific disorders) were compared with patients' ages at PD diagnosis by using t tests. Onset ages for major depressive disorder (MDD), generalized anxiety disorder (GAD), and panic disorder were compared with typical onset ages in the general population by using the sign test. A total of 108 patients (66.7% men; age 63.7 years [SD=8.9]) were included in the analysis.

RESULTS

Anxiety and depressive disorders occurred significantly earlier than PD diagnoses. Among patients whose anxiety and depression predated motor symptoms, the mean age at onset of anxiety disorders was 25.6 years earlier, and the mean age at onset of depressive disorders was 17.6 years earlier compared with the mean age at PD diagnosis (both p values <0.0001). Median onset ages for MDD (p<0.0001), GAD (p=0.0002), and panic disorder (p=0.0005) were significantly higher than typical median onset ages in the general population.

CONCLUSIONS

These results may indicate that neurodegenerative changes are present in parts of the brainstem reticular core and limbic system before motor circuits are affected to a degree that causes motor symptoms. Psychiatrists should be mindful that onset of MDD, GAD, and panic disorder after age 45 might signal a neurodegenerative movement disorder such as PD.

Stress and cortisol in Parkinson's disease

Stress is ubiquitous with many factors contributing to its effects, including psychological responses and associated biological factors, including cortisol related physiological responses, and inflammation. Also in Parkinson's disease there is growing evidence for the role of stress in some key symptoms, even stretching to the prodromal stage. Here we discuss the possible contributions of the range and nature of stress in PD and we aim to summarize the current knowledge about the role of stress-related responses on motor and non-motor symptoms, the underlying pathophysiology, and the potential implications for treatment.

Comorbid neuropsychiatric and autonomic features in REM sleep behavior disorder

Objective

Our aim is to define the extent of comorbidities in order to improve clinical care of patients with idiopathic rapid eye movement sleep behavior disorder (iRBD) utilizing the REM Sleep Behavior Disorder Associations with Parkinson's Disease Study (RAPiDS) cohort.

Methods

Consecutive adult study participants with iRBD confirmed on polysomnogram (PSG) were prospectively recruited from the Weill Cornell Center for Sleep Medicine. Evaluations comprised multiple facets of sleep, neurological, autonomic, and psychiatric function.

Results

Participants evaluated included 30 individuals with iRBD, with mean 1.5 ± 2.3 years from PSG to neuropsychiatric evaluation. Mean age was 59.5 ± 16.0 years at time of PSG, and 6/30 were women. Urinary difficulties were reported in 14/30 (47%): slight 7 (23%), mild 4 (13%), moderate 2 (7%), and severe 1 (3.0%). Ten out of 29 (34%) had abnormal Montreal Cognitive Assessment (MoCA) scores and the mean was 26.5 ± 3.2. The distribution of MoCA scores was significantly associated with urinary problems insofar as the more severe urinary problems were, the lower the MoCA scores (p = 0.04).

Conclusions

In this RAPiDS cohort, we detected an unexpectedly high occurrence of non-motor dysfunction. Our results point to the need for screening patients with iRBD for complaints that are actionable, for example those affecting mood, cognition, urinary function, and bowel function. We propose the term RBD+ to be used to identify such individuals. For the quality of life in patients diagnosed with RBD, a closer look by the clinician should be enacted, with appropriate referrals and workup.

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Comorbidities in idiopathic rapid eye movement sleep behavior disorder (iRBD) is further defined.

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REM Sleep Behavior Disorder Associations with Parkinson's Disease Study (RAPiDS) cohort

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There was a high occurrence of non-motor dysfunction in this cohort.

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The need for screening patients with iRBD for complaints that are actionable was demonstrated.

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We proposed the term “RBD+” to be used to identify such individuals.

The Neuropsychiatry of Parkinson Disease: A Perfect Storm

Affective disorders, cognitive decline, and psychosis have long been recognized as common in Parkinson disease (PD), and other psychiatric disorders include impulse control disorders, anxiety symptoms, disorders of sleep and wakefulness, and apathy. Psychiatric aspects of PD are associated with numerous adverse outcomes, yet in spite of this and their frequent occurrence, there is incomplete understanding of epidemiology, presentation, risk factors, neural substrate, and management strategies. Psychiatric features are typically multimorbid, and there is great intra- and interindividual variability in presentation. The hallmark neuropathophysiological changes that occur in PD, plus the association between exposure to dopaminergic medications and certain psychiatric disorders, suggest a neurobiological basis for many psychiatric symptoms, although psychological factors are involved as well. There is evidence that psychiatric disorders in PD are still under-recognized and undertreated and although psychotropic medication use is common, controlled studies demonstrating efficacy and tolerability are largely lacking. Future research on neuropsychiatric complications in PD should be oriented toward determining modifiable correlates or risk factors and establishing efficacious and well-tolerated treatment strategies.

Early and Accurate Identification of Parkinson Disease Among US Veterans

Early and accurate identification and management of veterans at risk for Parkinson disease is an important priority area for the US Department of Veterans Affairs because of the substantial impact on quality of life and disability-adjusted life years.

Hyposmia as a Predictive Marker of Parkinson's Disease: A Systematic Review and Meta-Analysis

Background

Hyposmia is one of the most common and best-characterized conditions that is also one of the first nonmotor features of Parkinson's disease (PD). The association of hyposmia with PD is widely accepted; however the likelihood of developing PD is unclear. Our meta-analysis aimed to investigate the risk of PD in individuals with hyposmia.

Methods

Prospective studies on humans published before December 4^th, 2018, were searched for in PubMed, Embase, Web of Science, and Cochrane Library databases. Two independent reviewers screened studies for inclusion and extracted data. We assessed the quality of studies using the Newcastle–Ottawa Scale and pooled data for analysis using random-effects models.

Results

Of the 1774 studies retrieved, seven met the inclusion criteria for this review. A total of 3272 hyposmia and 176 PD events were reported over follow-up periods ranging from 3 to 17 years. Hyposmia was associated with a 3.84-fold risk of developing PD (pooled relative risk: 3.84, 95% CI 2.12−6.95). Subgroup analyses identified few differences between different hyposmia assessment methodologies and follow-up periods.

Conclusions

Our findings suggest that deficiencies in olfaction are associated with an increased risk of developing PD. Future studies are needed to investigate whether hyposmia is a promising and feasible biomarker for the early diagnosis of PD.

Parkinson's Disease is Associated with Dysregulations of a Dopamine-Modulated Gene Network Relevant to Sleep and Affective Neurobehaviors in the Striatum

In addition to the characteristic motor symptoms, Parkinson’s disease (PD) often involves a constellation of sleep and mood symptoms. However, the mechanisms underlying these comorbidities are largely unknown. We have previously reconstructed gene networks in the striatum of a population of (C57BL/6J x A/J) F2 mice and associated the networks to sleep and affective phenotypes, providing a resource for integrated analyses to investigate perturbed sleep and affective functions at the gene network level. Combining this resource with PD-relevant transcriptomic datasets from humans and mice, we identified four networks that showed elevated gene expression in PD patients, including a circadian clock and mitotic network that was altered similarly in mouse models of PD. We then utilized multiple types of omics data from public databases and linked this gene network to postsynaptic dopamine signaling in the striatum, CDK1-modulated transcriptional regulation, and the genetic susceptibility of PD. These findings suggest that dopamine deficiency, a key aspect of PD pathology, perturbs a circadian/mitotic gene network in striatal neurons. Since the normal functions of this network were relevant to sleep and affective behaviors, these findings implicate that dysregulation of functional gene networks may be involved in the emergence of non-motor symptoms in PD. Our analyses present a framework for integrating multi-omics data from diverse sources in mice and humans to reveal insights into comorbid symptoms of complex diseases.

Non-motor features of Parkinson's disease in a nested case-control study of US men

BACKGROUND

Several non-motor features may individually contribute to identify prodromal Parkinson's disease (PD), but little is known on how they interact.

METHODS

We conducted a case-control study nested within the Health Professionals Follow-up Study in a large cohort of men age 40-75 at recruitment in 1986. Cases (n=120) had confirmed PD, were<85 in January 2012, returned a 2012 questionnaire with questions on probable rapid eye movement sleep behaviour disorder (RBD) and constipation sent to all cohort participants and completed in 2014 the Brief Smell Identification Test and a questionnaire assessing parkinsonism and other non-motor PD features (including depressive symptoms, excessive daytime sleepiness, impaired colour vision and body pain). Controls (n=6479) met the same criteria as cases, except for the PD diagnosis.

RESULTS

Concurrent constipation, probable RBD and hyposmia were present in 29.3% of cases and 1.1% of controls, yielding an age-adjusted OR of 160(95%CI 72.8to353) for three features versus none. The odds of PD increased exponentially with additional non-motor features (OR for 6-7 features versus none: 1325; 95%CI333to5279). Among men without PD, the number of non-motor features was associated with odds of parkinsonism (OR for 6-7 features versus none: 89; 95%CI21.2to375). We estimated that in a population with a prodromal PD prevalence of 2%, concurrent constipation, probable RBD and hyposmia would have a maximum sensitivity of 29% and a positive predictive value (PPV) of 35%. The PPV could increase up to 70% by including additional features, but with sharply decreased sensitivity.

CONCLUSIONS

Concurrent constipation, probable RBD and hyposmia are strongly associated with PD. Because these features often precede motor symptoms and their co-occurrence could provide an efficient method for early PD identification.

Association between depression and the subsequent risk of Parkinson's disease: A meta-analysis

BACKGROUND

Observational studies, including recent large cohort studies, have reported an association between depression and the risk of Parkinson's disease (PD); however, conclusions were inconsistent. Clarifying this relation might improve the understanding of risk factors for and the disease mechanisms in PD. Therefore, we performed a meta-analysis to examine whether depression is associated with an increased risk of PD.

METHODS

A literature search in the PubMed, EMBASE, Scopus, PsycINFO and Web of Science databases was undertaken through March 2018, looking for observational studies evaluating the association between depression and the risk of PD. Pooled relative risk (RR) estimates and 95% confidence intervals (CIs) were calculated using a random-effects model. Subgroup analyses and sensitivity analyses were also performed.

RESULTS

A random-effects meta-analysis of 5 cohort studies and 6 case-control studies demonstrated a significant positive association between depression and a subsequent risk of PD (RR, 2.20; 95% CI, 1.87-2.58), and it was consistent across subgroups. Furthermore, sensitivity analysis confirmed the stability of the results; visual examination of funnel plots and Begg's and Egger's tests showed no evidence of publication bias.

CONCLUSIONS

Our meta-analysis demonstrated that persons with depression exhibited an increased risk of a subsequent PD diagnosis. The pathophysiological and psychological mechanisms underlying this association are still unclear and warrant further research.

Advances in markers of prodromal Parkinson disease

Efforts to develop neuroprotective therapy for Parkinson disease (PD) are focusing on the early stages of disease, which offer the best opportunity to intervene. Early PD can be divided into preclinical, prodromal and clinical stages; in this Review, we focus on the prodromal stage and markers that can be used to identify prodromal PD. We consider the necessary properties of a marker, before providing an overview of the proven and potential markers of prodromal PD, including clinical nonmotor markers, clinical motor markers, neuroimaging markers and tissue biomarkers. Markers for which the ability to predict conversion to PD is supported by the strongest evidence include olfactory loss, REM sleep behaviour disorder and constipation. Markers with the highest diagnostic strength include REM sleep behaviour disorder, dopaminergic imaging and subtle motor parkinsonism. The lead time - the period between the appearance of a marker and conversion to PD - is highly variable between markers, ranging from 5 years for impaired motor performance to >20 years for autonomic symptoms. The cost of screening for these markers also varies dramatically: some require just questionnaires, whereas others require sophisticated scanning techniques. Finally, we summarize how prodromal and risk markers can be combined to estimate the probability that an individual has prodromal PD, with a focus on the International Parkinson Disease and Movement Disorders Society (MDS) Prodromal Parkinson Criteria.

Neuropsychiatric Issues in Parkinson Disease

PURPOSE OF REVIEW

This article reviews the recognition and management of neuropsychiatric issues in Parkinson disease (PD), including mood disorders, cognitive impairment, and behavioral disturbances.

RECENT FINDINGS

Patients with PD frequently develop neuropsychiatric issues, and these issues can greatly affect their quality of life. In recent years, mood, cognitive, and behavioral issues in PD have received greater recognition, with increasing attention directed toward improved screening and therapeutic interventions for symptomatic treatment. Taken together as a group, neuropsychiatric issues can be found throughout the whole course of PD, from early in the disease, potentially even in a premotor stage, to the time of diagnosis and later in the course with more advanced disease.

SUMMARY

In the comprehensive care of patients with PD, recognition of neuropsychiatric issues is critical. Advances in therapeutics for the different neuropsychiatric symptoms are still needed, although several pharmacologic and nonpharmacologic options are available. Patient management frequently requires a multidisciplinary approach, with collaboration of neurologists with neuropsychologists, psychologists, psychiatrists, and other health professionals.

An Investigation on the Clinical Features and Neurochemical Changes in Parkinson's Disease With Depression

Objective: To investigate the clinical features and neurochemical changes in Parkinson's disease with depression (PD-D). Methods: A total of 478 PD patients were divided into PD-D and PD patients without depression (PD-ND) groups according to the 24-item Hamilton Depression Rating Scale (HAMD) score. Demographic variables, motor and non-motor symptoms and activities of daily living were evaluated. The independent influencing factors of PD-D were investigated via binary logistic regression analysis. The levels of neurotransmitters in cerebrospinal fluid (CSF) were measured and their correlations with HAMD score were analyzed. Results: The proportion of PD-D was 59.0%, of which 76.95, 20.92, and 2.13% had mild, moderate, and severe depression, respectively. Anxiety/somatization was the most prevalent sub-factor of HAMD in PD-D. The scores of UPDRS III, postural instability/gait difficulty (PIGD) type and the scores of 14-item Hamilton Anxiety Scale (HAMA) and 14-item Chalder Fatigue Scale (FS) were independently associated with PD-D. The levels of dopamine (DA) and 5-hydroxytryptamine (5-HT) were all significantly reduced in PD-D group compared with those in PD-ND group. HAMD scores were negatively correlated with the DA levels in CSF. Conclusions: PD patients have a high proportion of depression, mainly of mild and moderate levels. The profile of depression in PD population is subtly different from that of the general population. Motor symptoms, PIGD type, anxiety and fatigue are the significant influencing factors of PD-D. Compared to 5-HT, DA may play a more important role in PD-D.

Biological and Clinical Implications of Comorbidities in Parkinson's Disease

A wide spectrum of comorbidities has been associated with Parkinson's disease (PD), a progressive neurodegenerative disease that affects more than seven million people worldwide. Emerging evidence indicates that chronic diseases including diabetes, depression, anemia and cancer may be implicated in the pathogenesis and progression of PD. Recent epidemiological studies suggest that some of these comorbidities may increase the risk of PD and precede the onset of motor symptoms. Further, drugs to treat diabetes and cancer have elicited neuroprotective effects in PD models. Nonetheless, the mechanisms underlying the occurrence of these comorbidities remain elusive. Herein, we discuss the biological and clinical implications of comorbidities in the pathogenesis, progression, and clinical management, with an emphasis on personalized medicine applications for PD.

Nonmotor symptoms and Parkinson disease in United States farmers and spouses

Objectives

Few studies have evaluated the presence of multiple nonmotor symptoms (NMS) in relation to Parkinson disease (PD). Therefore, we examined cross-sectional associations between individual and multiple NMS and PD in the Agricultural Health Study.

Methods

20,473 male farmers and 16,259 female spouses provided information on six NMS (reduced sense of smell, dream-enacting behavior, daytime sleepiness, infrequent bowel movement, depression, and anxiety) in the cohort’s 2013–2015 follow-up survey. 191 men and 68 women reported physician-diagnosed PD. We estimated odds ratios (ORs) and 95% confidence intervals (CIs) using multivariable logistic regression models separately by sex.

Results

NMS were each associated with PD, with the strongest association for reduced sense of smell in men and dream-enacting behavior in women. The number of NMS showed a strong dose-response relationship with PD, particularly in men. ORs were 5.5 (95% CI 3.4–8.8) for one, 17 (95% CI 10.4–28.0) for two, and 53.4 (95% CI 33.2–86.1) for three or more NMS in men; the corresponding ORs were 4.6 (95% CI 2.3–9.5), 6.7 (95% CI 2.9–15.6), and 23.6 (95% CI 10.7–52.4) in women (P_{NMS-interaction-with-sex} = 0.07).

Conclusions

The number of NMS was associated with PD in a dose-response manner and the association appeared stronger in men than in women. These findings should be further investigated in population-based prospective studies.

Epidemiology, environmental risk factors and genetics of Parkinson's disease

Parkinson's disease (PD) is a frequent neurodegenerative disease with a premotor phase that lasts several years. Risk factors that have been linked to PD are tobacco, caffeine, black tea, pesticides and calcium channel blockers. Some risk factors may be due to inverse causality (e.g. changes in personality during the premotor phase). The genetics of PD are complex with a contribution of Mendelian (e.g. SNCA, LRRK2, Parkin, Pink1,…) and non-Mendelian factors (e.g. single nucleotide polymorphisms). Glucocerebrosidase gene mutations (Gaucher disease) are currently the strongest genetic risk factor for PD. Studying risk factors will help to better understand the pathogenesis of PD.

Association between gene polymorphism and depression in Parkinson's disease: A case-control study

OBJECTIVE

To investigate possible associations of Parkinson's disease (PD) with polymorphism in depression-related genes and in the alpha-synuclein (SNCA) gene.

METHODS

A consecutive series of patients with PD were divided into those with depression and those without it. Patients (330) were genotyped at four single-nucleotide polymorphisms (SNPs) in four genes previously associated with depression, as well as four SNPs in the PD-associated SNCA gene.

RESULTS

Of 330 patients, 125 (37.9%) had depression and 205 (62.1%) did not. Univariate analysis revealed significant differences between the two groups in minor allele frequency at the SNP rs1545843 in the SLC6A15 gene (p<0.05), as well as in frequencies of genotypes and minor alleles at rs78162420 in the TPH2 gene (all p<0.05). Logistic regression identified the following risk factors for depression among patients with PD: Hoehn and Yahr stage>2 (OR 1.759, 95%CI 1.035-2.989, p=0.037), AA genotype at rs1545843 (OR 1.866, 95%CI 1.017-3.426, p=0.044), and AC genotype at rs78162420 (OR 5.036, 95%CI 1.451-17.484, p=0.011).

CONCLUSIONS

Among patients with PD, depression is associated with polymorphism at rs78162420 and rs1545843, both previously linked with depression. Our results may help clarify the pathogenesis of depression in PD.

Neuropsychiatric symptoms in untreated Parkinson's disease

Neuropsychiatric and cognitive symptoms are common in Parkinson's disease (PD) and may precede and exceed motor symptoms as major factors impacting disease course and quality of life. Neuropsychiatric symptoms (NPS) in PD are various and are attributed to pathologic changes within multiple brain regions, to psychological stress, and to adverse effects of dopamine replacement therapy. Sleep disorders and mood symptoms such as apathy, depression, and anxiety may antedate the development of motor symptoms by years, while other NPS such as impulse control disorders, psychosis, and cognitive impairment are more common in later stages of the disease. Few studies report on NPS in the early, untreated phase of PD. We reviewed the current literature on NPS in PD with a focus on the early, drug-naive stages of PD. Among these early disease stages, premotor and early motor phases were separately addressed in our review, highlighting the underlying pathophysiological mechanisms as well as epidemiological characteristics, clinical features, risk factors, and available techniques of clinical assessment.

Integrative transcriptomic meta-analysis of Parkinson's disease and depression identifies NAMPT as a potential blood biomarker for de novo Parkinson's disease

Emerging research indicates that depression could be one of the earliest prodromal symptoms or risk factors associated with the pathogenesis of Parkinson’s disease (PD), the second most common neurodegenerative disorder worldwide, but the mechanisms underlying the association between both diseases remains unknown. Understanding the molecular networks linking these diseases could facilitate the discovery of novel diagnostic and therapeutics. Transcriptomic meta-analysis and network analysis of blood microarrays from untreated patients with PD and depression identified genes enriched in pathways related to the immune system, metabolism of lipids, glucose, fatty acids, nicotinamide, lysosome, insulin signaling and type 1 diabetes. Nicotinamide phosphoribosyltransferase (NAMPT), an adipokine that plays a role in lipid and glucose metabolism, was identified as the most significant dysregulated gene. Relative abundance of NAMPT was upregulated in blood of 99 early stage and drug-naïve PD patients compared to 101 healthy controls (HC) nested in the cross-sectional Parkinson’s Progression Markers Initiative (PPMI). Thus, here we demonstrate that shared molecular networks between PD and depression provide an additional source of biologically relevant biomarkers. Evaluation of NAMPT in a larger prospective longitudinal study including samples from other neurodegenerative diseases, and patients at risk of PD is warranted.

MDS research criteria for prodromal Parkinson's disease

This article describes research criteria and probability methodology for the diagnosis of prodromal PD. Prodromal disease refers to the stage wherein early symptoms or signs of PD neurodegeneration are present, but classic clinical diagnosis based on fully evolved motor parkinsonism is not yet possible. Given the lack of clear neuroprotective/disease-modifying therapy for prodromal PD, these criteria were developed for research purposes only. The criteria are based upon the likelihood of prodromal disease being present with probable prodromal PD defined as ≥80% certainty. Certainty estimates rely upon calculation of an individual's risk of having prodromal PD, using a Bayesian naïve classifier. In this methodology, a previous probability of prodromal disease is delineated based upon age. Then, the probability of prodromal PD is calculated by adding diagnostic information, expressed as likelihood ratios. This diagnostic information combines estimates of background risk (from environmental risk factors and genetic findings) and results of diagnostic marker testing. In order to be included, diagnostic markers had to have prospective evidence documenting ability to predict clinical PD. They include motor and nonmotor clinical symptoms, clinical signs, and ancillary diagnostic tests. These criteria represent a first step in the formal delineation of early stages of PD and will require constant updating as more information becomes available.

Prodromal Markers in Parkinson's Disease: Limitations in Longitudinal Studies and Lessons Learned

A growing body of evidence supports a prodromal neurodegenerative process preceding the clinical onset of Parkinson's disease (PD). Studies have identified several different prodromal markers that may have the potential to predict the conversion from healthy to clinical PD but use considerably different approaches. We systematically reviewed 35 longitudinal studies reporting prodromal PD features and evaluated the methodological quality across 10 different predefined domains. We found limitations in the following domains: PD diagnosis (57% of studies), prodromal marker assessments (51%), temporal information on prodromal markers or PD diagnosis (34%), generalizability of results (17%), statistical methods (accounting for at least age as confounder; 17%), study design (14%), and sample size (9%). However, no limitations regarding drop-out (or bias investigation), or report of inclusion/exclusion criteria or prodromal marker associations were revealed. Lessons learned from these limitations and additional aspects of current prodromal marker studies in PD are discussed to provide a basis for the evaluation of findings and the improvement of future research in prodromal PD. The observed heterogeneity of studies, limitations and analyses might be addressed in future longitudinal studies using a, yet to be established, modular minimal set of assessments improving comparability of findings and enabling data sharing and combined analyses across studies.

Onset and progression factors in Parkinson's disease: A systematic review

Current research has identified several factors thought to be associated with the onset and progression of Parkinson's Disease (PD); however, whether certain factors contribute to or are protective against PD remains unclear. As such, a systematic search of the literature was performed using variations of MeSH and keyword search terms to identify and summarize systematic reviews and primary studies pertaining to factors associated with the onset and progression of PD. Factors referred to both traditional risk factors and prodromal markers. The following databases were searched: MEDLINE, MEDLINE In-Process, EMBASE, PsycINFO, Scopus, Web of Science, Cochrane Database of Systematic Reviews, Cumulative Index to Nursing and Allied Health Literature (CINAHL), ProQuest Dissertations & Theses, AARP AgeLine, and PDGene. A quality assessment of included systematic reviews was completed using the validated Assessment of the Methodological Quality of Systematic Reviews (AMSTAR) tool. Data extraction targeted reported factors, risk estimates, and 95% confidence intervals (CI). Findings identified 11 systematic reviews of sufficient quality reporting factors for PD onset, and no systematic reviews reporting factors for PD progression. In addition, 93 primary articles were identified, of which, 89 articles addressed factors related to PD onset and 4 articles addressed factors related to the PD progression. Pesticide exposure, rural living, well-water drinking, and farming occupation were consistently found to be positively associated with the onset of PD. Moreover, family history and polymorphisms to key genes were also found to be positively associated with the onset of PD. Conversely, coffee consumption, cigarette smoking, and some polymorphisms were consistently found to be negatively associated with the onset of PD. Urate was the only identified factor linked to the progression of PD; it was mostly found to be negatively associated with PD. In sum, the evidence was systematically found and summarized in the literature pertaining to factors related to the onset and progression of PD.

Adaptive down-regulation of the serotonin transporter in the 6-hydroxydopamine-induced rat model of preclinical stages of Parkinson's disease and after chronic pramipexole treatment

Our recent study has indicated that a moderate lesion induced by bilateral 6-hydroxydopamine (6-OHDA) injections into the ventrolateral region of the caudate-putamen (CP) in rats, modeling preclinical stages of Parkinson's disease, induces a "depressive-like" behavior which is reversed by chronic treatment with pramipexole (PRA). The aim of the present study was to examine the influence of the above lesion and chronic PRA treatment on binding to the serotonin transporter (SERT) in different brain regions. As before, 6-OHDA (15 μg/2.5 μl) was administered bilaterally into the CP. PRA (1mg/kg) was injected subcutaneously twice a day for 2 weeks. Serotonergic and dopaminergic neurons of the dorsal raphe (DR) were immunostained for tryptophan hydroxylase and tyrosine hydroxylase, respectively, and were counted stereologically. Binding of [(3)H]GBR 12,935 to the dopamine transporter (DAT) and [(3)H]citalopram to SERT was analyzed autoradiographically. Intrastriatal 6-OHDA injections decreased the number of dopaminergic, but not serotonergic neurons in the DR. 6-OHDA reduced the DAT binding in the CP, and SERT binding in the nigrostriatal system (CP, substantia nigra (SN)), limbic system (ventral tegmental area (VTA), nucleus accumbens (NAC), amygdala, prefrontal cortex (PFCX), habenula, hippocampus) and DR. A significant positive correlation was found between DAT and SERT binding in the CP. Chronic PRA did not influence DAT binding but reduced SERT binding in the above structures, and deepened the lesion-induced losses in the core region of the NAC, SN, VTA and PFCX. The present study indicates that both the lesion of dopaminergic neurons and chronic PRA administration induce adaptive down-regulation of SERT binding. Moreover, although involvement of stimulation of dopaminergic transmission by chronic PRA in its "antidepressant" effect seems to be prevalent, additional contribution of SERT inhibition cannot be excluded.