Motor, behavioural, and cognitive correlates of fatigue in early, de novo Parkinson disease patients

The Impact of Fatigue on Sleep and Other Non-Motor Symptoms in Parkinson's Disease

Fatigue is a common non-motor symptom in Parkinson's disease (PD), but even so, it may still be underdiagnosed or misdiagnosed in current practice due to its non-specific manifestations. The aims of this study were to investigate the prevalence of fatigue in PD patients compared to healthy controls and to identify the main characteristics and associations of fatigue with other non-motor symptoms and the impact of fatigue on sleep disturbances in Parkinson's disease.

MATERIALS AND METHODS

case-control study in which 131 PD patients and 131 age- and sex-matched controls were enrolled. Main characteristics of fatigue, sleep, and other non-motor symptoms were assessed using specific validated questionnaires.

RESULTS

According to the Chalder fatigue scale, fatigue is more prevalent in PD patients (38.16%) compared to healthy controls (26.71%). Fatigue was identified in 46.54% of the PD patients using the Parkinson's Fatigue Scale (PFS-16). PD patients with fatigue presented a worse motor status, more sleep disturbances (insomnia, daytime sleepiness), a broader spectrum of non-motor symptoms (pain, anxiety, urinary disturbances), worse cognitive performances, a lower level of happiness, and worse quality of life compared to PD patients without fatigue.

CONCLUSION

Fatigue is a common symptom of PD and needs to be assessed, considering its consequences on quality of life. Sleep disturbances have a great influence over fatigue in PD patients.

Role of selective attention in fatigue in neurological disorders

BACKGROUND

Chronic fatigue is a significant symptom in several diseases including traumatic and degenerative neurological disorders. While several studies have investigated the correlates of chronic fatigue, there is as yet no unifying framework to explain chronic fatigue.

METHODS

In this narrative review, I investigate the role of selective attention in the development of chronic fatigue and discuss results within the framework of the sensory attenuation model of fatigue, which posits that fatigue is the phenomenological output of altered attention to sensory input. Following a short introduction of this framework, I present results from investigations that address attentional mechanisms in fatigue in multiple sclerosis, stroke, traumatic brain injury and Parkinson's disease.

RESULTS

Attention was quantified in all four disease models using a variety of outcome measures, including behavioural, neurophysiological, structural and functional brain connectivity. The range of measures precluded direct comparison of results across disease conditions; however, in all four disease models there was evidence of poor selective attention that explained levels of chronic fatigue, supporting the sensory attenuation model of fatigue as a disease-independent mechanism of fatigue. Evidence was lacking to draw any conclusions about the direction of causality.

CONCLUSION

The role of selective attention in development of fatigue is indicated. Future studies must focus on establishing causality and exploring attentional circuitry as a potential therapeutic target.

Poor sleep quality is associated with fatigue and depression in early Parkinson's disease: A longitudinal study in the PALS cohort

Background

Sleep disorders are common in Parkinson's disease (PD). However, the longitudinal relationship between sleep quality and the other non-motor symptoms of PD has not been well characterized, especially in early PD.

Objective

To explore the value of baseline sleep quality in predicting the progression of other non-motor symptoms in early PD.

Methods

109 early PD patients were recruited to the study. Patients were stratified into good and poor sleepers using the Pittsburgh Sleep Quality Index (PSQI). Assessments performed at baseline and 1 year follow-up included the Epworth Sleepiness Scale, Fatigue Severity Scale, Non-Motor Symptom Scale, Geriatric Depression Scale, Hospital Anxiety and Depression Scale, Apathy Scale, Montreal Cognitive Assessment and detailed neuropsychological assessments. Multivariable linear regression was performed at baseline to investigate differences in clinical scores between poor and good sleepers, while multivariable regression models were used to investigate associations between sleep quality and progression of test scores at 1 year follow-up.

Results

59 poor sleepers and 50 good sleepers were identified. At baseline, poor sleepers had greater HADS anxiety scores (p = 0.013) [2.99 (95% CI 2.26, 3.73)] than good sleepers [1.59 (95% CI 0.75, 2.42)]. After 1 year, poor sleepers had greater fatigue (FSS scores +3.60 as compared to −2.93 in good sleepers, p = 0.007) and depression (GDS scores +0.42 as compared to −0.70, p = 0.006).

Conclusion

This study shows a longitudinal association between sleep quality, fatigue, and depression in early PD patients, independent of medication effect and disease severity, this may support the hypothesis that a common serotonergic pathway is implicated in these non-motor symptoms.

Fatigue in de novo Parkinson's Disease: Expanding the Neuropsychiatric Triad?

BACKGROUND

Fatigue is a frequent and troublesome symptom present from the early stages of Parkinson's disease (PD).

OBJECTIVE

To examine the relationship between fatigue and the neuropsychiatric triad, which includes apathy, depression, and anxiety, in de novo PD.

METHODS

We performed a cross-sectional study including 197 patients with de novo PD and assessed fatigue using the Parkinson's Disease Fatigue Scale (PDFS-16). We evaluated motor status using the Unified Parkinson's Disease Rating Scale (UPDRS) part III score and evaluated neuropsychiatric status using the Ardouin Scale of Behavior in Parkinson's Disease (ASBPD). We carried out univariate and multivariate analyses to model association between motor signs, non-motor signs, and fatigue risk.

RESULTS

Frequency of fatigue (28.9%) was of the same order of magnitude as that of apathy. PD patients with fatigue reported a lower quality of life than patients without fatigue (p < 0.0001). The ASBPD showed that patients with fatigue had higher scores for depressed mood (p < 0.0001), anxiety (p < 0.0001), and apathy (p < 0.0001). In the univariate analysis, fatigue score was positively correlated with apathy, depression, anxiety, and the neuropsychiatric triad as a whole, and to a lesser extent with female sex, hyperemotivity, and the UPDRS part III score. In the multivariate analysis, after adjusting for sex and motor status, the fatigue score remained significantly correlated with apathy (OR = 11.17 [4.33-28.78], p < 0.0001) and depression (OR = 4.28 [1.39-13.12], p = 0.01), but not with anxiety (OR = 0.94 [0.34-2.58], p = 0.9).

CONCLUSION

We propose that the neuropsychiatric triad could be expanded to include fatigue.

Progression of Fatigue in Early Parkinson's Disease: A 3-Year Prospective Cohort Study

Objective: To explore the frequency, evolution, associated factors, and risk factors of fatigue over 3-year of prospective follow-up in a cohort of patients with early Parkinson’s disease (PD).

Methods: A total of 174 PD patients in the early stage were enrolled and quantitively assessed motor and non-motor symptoms using comprehensive scales including the Fatigue Severity Scale (FSS) annually. Each subject was categorized as PD with and without fatigue based on a cut-off mean value of 4 using FSS. The generalized estimating equation (GEE) was utilized to investigate the associated factors, and the stepwise binary logistic regression model was performed to explore the predictors.

Results: The frequency of fatigue was slightly changed (ranging from 35.1 to 40.4%) during the 3-year follow-up. The changed pattern of the frequency of fatigue was similar to that of anxiety. Fatigue was significantly associated with nocturnal sleep disorders (B 2.446, P < 0.001), high Hamilton Anxiety Rating Scale (HAMA) score (B 1.072, P = 0.011), and high Unified PD Rating Scale (UPDRS) III score (B 1.029, P = 0.003) over time. High UPDRS III score [odds ratio (OR) 1.051, P = 0.015] at baseline increased the risk of developing fatigue after 1-year; high LEDD (OR 1.002, P = 0.037) increased the risk of developing fatigue after 2-year; and high LEDD (OR 1.003, P = 0.049) and high HAMA score (OR 1.077, P = 0.042) increased the risk of developing fatigue after 3-year.

Conclusion: Our present study provided evidence of the longitudinal evolution of fatigue in patients with early PD and help clinical management of fatigue.

Merging Yoga and Occupational Therapy for Parkinson’s Disease improves fatigue management and activity and participation measures

Introduction

The purpose of this study was to explore the influence of a falls-risk management intervention, Merging Yoga and Occupational Therapy for Parkinson’s Disease, on fatigue and activity and participation measures, as well as examine the relationship between these constructs.

Methods

This mixed methods study included 17 participants with Parkinson’s disease. Participants took the Modified Fatigue Impact Scale and the International Classification of Functioning, Disability, and Health Measure of Participation and Activities Screener at three 8-week intervals: baseline (followed by an 8-week control period), pre-intervention, and post-intervention. Focus groups were completed at the conclusion of the study to explore participants’ perception of Merging Yoga and Occupational Therapy for Parkinson’s Disease related to their fatigue and activity and participation.

Results

Fatigue and activity and participation measures were significantly correlated ( r = 0.76). Activity and participation measures (Measure of Participation and Activities Screener) significantly improved after the intervention ( p = 0.012). Four themes related to fatigue and/or activity and participation emerged following qualitative analysis, including: managing fatigue: paying attention and acting accordingly; creating mindfulness in daily activities; giving and receiving within a community; and strengthening relationship to self and others.

Conclusion

Participants experienced improvement in activity and participation measures and perceived fatigue management after engagement in the community-based Merging Yoga and Occupational Therapy for Parkinson’s Disease program.

The Relationship Between Anxiety Disorders and Parkinson's Disease: Clinical and Therapeutic Issues

PURPOSE OF REVIEW

This paper seeks to describe anxiety's different symptomatologic presentations in Parkinson's disease (PD), its longitudinal course and predictors, as well as its motor and non-motor correlates. It also reviews the available screening tools and different treatment modalities.

RECENT FINDINGS

In PD, longitudinal predictors of anxiety are mostly non-motor non-dopaminergic symptoms. The longitudinal course of anxiety is mainly a stable one. The Parkinson Anxiety Scale and the Geriatric Anxiety Scale are the 2 recommended screening tools. A third of PD patients suffer from an anxiety disorder at any time point. It can precede or follow PD motor symptoms. Anxiety is associated with demographic, disease-related motor and non-motor features. There is a lack of studies evaluating psychotropic treatment of anxiety in PD. Adjustment of dopaminergic treatment is indicated when anxiety is associated with motor fluctuations. DBS can be useful as well as CBT and body-mind interventions.

Non-motor impairments affect walking kinematics in Parkinson disease patients: A cross-sectional study

BACKGROUND

In patients with Parkinson disease (PD), severe postural and gait impairments are rarely observed in early stage of disease and non-motor symptoms (NMS) are often overlooked.

OBJECTIVE

This observational study aimed to characterize the impact of non-motor impairments on walking kinematics in early stages PD patients, and to assess the differences of gait parameters and NMS between PD patients with and without mild cognitive impairment (MCI).

METHODS

Twenty-six patients with Modified Hoehn and Yahr Scale score≤2 were evaluated for NMS using Kings Parkinson's Pain Scale, Parkinson Fatigue Severity scale, Parkinson Anxiety Scale, Beck Depression Inventory and Epworth Sleepiness Scale, kinematic parameters through an inertial sensor and cognitive performance by a comprehensive neuropsychological battery.

RESULTS

Fatigue had a moderate negative correlation with step cadence, and a moderate to strong positive correlation with gait duration, Timed Up and Go (TUG) and TUG Dual Task (p < 0.01). Pain showed positive moderate correlation with gait duration (p < 0.01). Twelve patients resulted affected by MCI and reported significantly worse scores in gait duration, pain and fatigue (p < 0.05). According to cognitive z scores, PD-MCI group showed a moderate negative correlation between visuospatial abilities and fatigue (p < 0.05).

CONCLUSIONS

NMS significantly affect walking kinematics whereas a limited role of cognitive status on motor performance occur in the early PD stages.

Sleep Disturbances and Associated Factors in Drug-Naïve Patients with Parkinson's Disease

PURPOSE

Sleep disturbance is one of the common symptoms in Parkinson's disease (PD). The study of sleep disturbance used to concentrate on treated PD. This study aimed to investigate the factors that are associated with the sleep quality of drug-naïve patients with PD.

PATIENTS AND METHODS

All participants were interviewed using a standard questionnaire to collect basic information. PD severity, depression symptoms, anxiety symptoms, sleep quality, cognitive status, life quality, and the presence of rapid eye movement (REM) sleep behavior disorder (RBD) and minor hallucination were assessed using corresponding rating scales. The patients with a Pittsburgh Sleep Quality Index score ≤6 fell into the poor sleep group, and those with REM Sleep Behavior Disorder Screening Questionnaire score ≥5 were considered to have probable RBD.

RESULTS

Seventy drug-naive patients with PD and 30 healthy controls matched for age, sex, and education were recruited. Up to 41.4% of the patients suffered from sleep disturbance, and 24.3% of the patients had RBD. Poor sleepers were more likely to have left-side predominant motor symptoms. Compared with good sleepers, poor sleepers, particularly female patients, had more burden in the aspect of anxiety and depression. RBD was associated with more nonmotor symptoms, poor sleep quality, bad performance in cognition orientation domain, anxiety, depression, presence of minor hallucination, and poor life quality.

CONCLUSION

Sleep disturbances are common in drug-naïve PD and require wide attention. Motor symptom laterality and gender difference in mood are associated with sleep quality. Depression, anxiety, and RBD are highly related to sleep disturbance. RBD has many comorbidities, which can influence the cognitive function and life quality of the patients.

Correlates of Psychological Distress in Patients with Parkinson's Disease During the COVID-19 Outbreak

BACKGROUND

Following the severe consequences of the COVID-19 outbreak, on March 9, 2020, the Italian government implemented extraordinary measures to limit viral transmission, including restrictive quarantine measures. This resulted in a rapid and profound change of people's daily lives.

OBJECTIVE

We assessed the psychological impact of the 40-day quarantine in a large cohort of patients with Parkinson's disease (PD) and caregivers. Moreover, we analyzed whether prelockdown clinical features may be associated with subjective response of patients with PD to this traumatic event.

METHODS

A total of 94 patients with PD were enrolled in the study. The Impact of Event Scale-Revised, the Kessler Psychological Distress Scale, and the 12-item Zarit Burden Inventory were obtained from patients and caregivers by email. A multivariate regression analysis was performed to determine whether prelockdown clinical motor and nonmotor features were associated with the psychological impact of lockdown.

RESULTS

Regression analyses showed that prelockdown levels of anxiety, treatment-related motor complications, patients' quality of life, and lockdown hours per day were significantly associated with psychological impact measures of the 40-day quarantine. In addition, we showed that caregiver burden was correlated with overall patient autonomy and attention/memory impairment.

CONCLUSIONS

We identified specific PD motor and nonmotor features potentially predisposing to higher psychological impact of stressful situations, such as quarantine. This may help guide postpandemic interventions and preventive strategies to avoid further impairment of psychological well-being in patients with PD.

Fatigue correlates with sleep disturbances in Parkinson disease

BACKGROUND

Many Parkinson disease (PD) patients complain about chronic fatigue and sleep disturbances during the night. The objective of this study is to determine the relationship between fatigue and sleep disturbances by using polysomnography (PSG) in PD patients.

METHODS

Two hundred and thirty-two PD patients (152 with mild fatigue and 80 with severe fatigue) were recruited in this study. Demographic information and clinical symptoms were collected. Fatigue severity scale (FSS) was applied to evaluate the severity of fatigue, and PSG was conducted in all PD patients. FSS ≥4 was defined as severe fatigue, and FSS <4 was defined as mild fatigue. Multivariate logistic regression and linear regression models were used to investigate the associations between fatigue and sleep disturbances.

RESULTS

Patients with severe fatigue tended to have a longer duration of disease, higher Unified Parkinson Disease Rating Scale score, more advanced Hoehn and Yahr stage, higher daily levodopa equivalent dose, worse depression, anxiety, and higher daytime sleepiness score. In addition, they had lower percentage of rapid eye movement (REM) sleep (P = 0.009) and were more likely to have REM sleep behavior disorder (RBD) (P = 0.018). Multivariate logistic regression analyses found that the presence of RBD and proportion of REM sleep were the independent predictors for fatigue. After the adjustment of age, sex, duration, body mass index, severity of disease, scores of Hamilton Rating Scale for Depression, Hamilton Anxiety Rating Scale, and other sleep disorders, proportion of REM sleep and degree of REM sleep without atonia in patients with PD were still associated with FSS score.

CONCLUSION

Considering the association between fatigue, RBD, and the altered sleep architecture, fatigue is a special subtype in PD and more studies should be focused on this debilitating symptom.

Connectivity Correlates of Anxiety Symptoms in Drug-Naive Parkinson's Disease Patients

BACKGROUND

Anxiety symptoms are common in Parkinson's disease (PD). A link between anxiety and cognitive impairment in PD has been demonstrated.

OBJECTIVES

Using resting-state functional magnetic resonance imaging, we investigated intrinsic brain network connectivity correlates of anxiety symptoms in a cohort of drug-naive, cognitively unimpaired patients with PD.

METHODS

The intrinsic functional brain connectivity of 25 drug-naive, cognitively unimpaired PD patients with anxiety, 25 without anxiety, and 20 matched healthy controls was compared. All patients underwent a detailed behavioral and neuropsychological evaluation. Anxiety presence and severity were assessed using the Parkinson's Disease Anxiety Scale. Single-subject and group-level independent component analyses were used to investigate functional connectivity differences within and between the major resting-state networks.

RESULTS

Decreased connectivity within the default-mode and sensorimotor networks (SMN), increased connectivity within the executive-control network (ECN), and divergent connectivity measures within salience and frontoparietal networks (SN and FPN) were detected in PD patients with anxiety compared with those without anxiety. Moreover, patients with anxiety showed a disrupted inter-network connectivity between SN and SMN, ECN, and FPN. Anxiety severity was correlated with functional abnormalities within these networks.

CONCLUSIONS

Our findings demonstrated that an abnormal intrinsic connectivity within and between the most reported large-scale networks may represent a potential neural correlate of anxiety symptoms in drug-naive PD patients even in the absence of clinically relevant cognitive impairment. We hypothesize that these specific cognitive and limbic network architecture changes may represent a potential biomarker of treatment response in clinical trials. © 2020 International Parkinson and Movement Disorder Society.

Predictors of fatigue severity in early, de novo Parkinson disease patients: A 1-year longitudinal study

INTRODUCTION

Fatigue is one of the most common and disabling nonmotor symptom in Parkinson's disease (PD). The aim of the present study was to investigate the 1-year course of fatigue in a consecutive sample of de novo drug-naïve patients with PD, and at systematically searching for baseline motor and nonmotor predictors associated with fatigue severity over time.

METHODS

Fifty-five consecutive de novo PD patients (age: 64.71 ± 7.74 years) underwent a comprehensive examination, including Parkinson Fatigue Scale, Epworth Sleepiness Scale, Parkinson's Disease Sleep Scale, Beck Depression Inventory, Parkinson's Anxiety Scale, Apathy Evaluation Scale, and an extensive neuropsychological evaluation. Bivariate and multiple regression analyses were performed to identify baseline predictors independently related to fatigue severity at 1-year follow-up.

RESULTS

Prevalence rate of fatigue (defined by PFS cut-off) increased from 22% at baseline to 38% at 1-year follow-up. A similar increase in prevalence was observed for excessive daytime sleepiness, and apathy. Among patients with fatigue at baseline, 91% had fatigue at follow-up too (i.e., persistent fatigue). Multivariate regression analysis identified fatigue (p < 0.01), daytime sleepiness (p < 0.01), and emotional apathy (p < 0.01) as the main baseline variables significantly predicting fatigue severity at 1-year follow-up.

CONCLUSION

In early PD, fatigue increases and persists over time, and its severity is related to higher baseline levels of fatigue, excessive daytime sleepiness, and emotional apathy. These results warrant to monitor fatigue since the early stage of disease, and suggest that treating excessive daytime sleepiness and emotional apathy might prevent its worsening.

Effect of Olfactory and Gustatory Dysfunction and Motor Symptoms on Body Weight in Patients with Parkinson's Disease

BACKGROUND

Non-motor symptoms in Parkinson's disease (PD) are often associated with a negative impact on the patients' quality of life and on their weight regulation. The aim of this study was to assess the effect of olfactory and gustatory dysfunction, apathy, fatigue, depression, and motor symptoms on weight regulation in PD patients.

METHODS

We analyzed 112 participants, 63 PD patients (mean age ± SD: 69.2 ± 10.1), and 49 controls (mean age ± SD: 68 ± 9.6). For each participant we collected age, weight, height, BMI, olfactory and gustatory function, cognitive performance, apathy and fatigue.

RESULTS

Our data showed that 61.9% (n = 39) of PD patients had hyposmia, while 38.1% (n = 24) had anosmia. In PD patients, we observed a significant effect of Unified Parkinson's Disease Rating Scale (UPDRS), apathy, odor threshold, sweet perception and fatigue on weight regulation. Instead, there was no significant effect for depression and levodopa equivalent daily dosage (LEDD).

CONCLUSION

Our results suggest that PD non-motor symptoms such as olfactory/gustatory deficits and mood disorders may influence body weight.

Validation study of the Parkinson's Fatigue Scale in advanced Parkinson's disease

Purpose: To validate the Parkinson’s Fatigue Scale (PFS-16) in advanced Parkinson Disease (APD) patients using the scale’s Spanish version.

Patients and methods: In a clinical study for Levodopa-Carbidopa Intestinal Gel (LCIG), 59 patients were assessed over six months using the PFS-16 and other instruments. The psychometric properties of the PFS-16 were then analyzed.

Results: Patients (60.7% men) were aged 68.02±7.43 years. PD duration was 12.57±5.97 years. Median Hoehn and Yahr (HY) stage of patients in “on” was 2 (range: 1–4). There were excellent data quality and acceptability for the PFS-16 as a whole, except for moderate-to-high ceiling effects in its items. Two factors explained 67% of the variance, yet parallel analysis demonstrated the unidimensional nature of the PFS-16, whose internal consistency was satisfactory (Cronbach’s alpha=0.93; item homogeneity coefficient=0.19, and item total-corrected correlations=0.50–0.84). PFS-16 total score showed moderate-to-high correlations with fatigue-specific questions within clinical tools, namely item 20 of the Beck Depression Inventory (r_S=0.65) and item 4 of the Non-Motor Symptoms Scale (r_S=0.33). Weak-to-moderate correlations were observed between the PFS-16 and measures of anxiety, depression, apathy, and quality of life. There were no significant differences in PFS-16 total scores when grouped by age, sex, time from diagnosis, HY, and CGI-S. After treatment with LCIG, the relative change in PFS-16 total score was −17.6% and the effect size (Cohen’s d) was 0.92. Moderate correlations between changes in the PFS-16 and several other clinical tools were also found.

Conclusion: In APD patients, the PFS-16 showed satisfactory acceptability, internal consistency, construct validity, and responsiveness.

Psychometric Properties of the Apathy Scale in Advanced Parkinson's Disease

Objectives

To assess the psychometric attributes of the Apathy Scale- (AS-) Spanish version in patients with advanced Parkinson's disease (APD).

Materials and Methods

Over 6 months, 61 patients participated in a clinical study of levodopa-carbidopa intestinal gel (LCIG) and were evaluated using the AS and other clinical tools. Various psychometric attributes of the AS were assessed.

Results

Patients (60.7% men) were aged 68.02 ± 7.43 years, with 12.57 ± 5.97 years from PD diagnosis. Median HY of patients in “on state” was 2 (range, 1–4), and mean levodopa equivalent daily dose was 1455.98 ± 456.00 mg. Overall, the parameters of feasibility/acceptability were satisfactory, except for a moderate-to-high floor effect in AS items but not in its total score (both 3.3%). Cronbach's alpha was 0.78, while item homogeneity coefficient was 0.21. Almost all items (11/14) reached acceptable item-total corrected correlations (r_S = 0.16–0.50). AS total score was moderately correlated with Beck Depression Inventory (0.34) and with Non-Motor Symptoms Scale domains 2 (sleep/fatigue, 0.35), 3 (mood/apathy, 0.56), and 5 (attention/memory, 0.41). There were no significant differences between AS total scores by established groups of sex, time from diagnosis, HY, and Clinical Global Impression-Severity Scale. Following LCIG treatment, there was no significant change in the AS total score. The relative change was 5.56%, the standard error of the difference was 4.17, and Cohen's d effect was 0.10.

Conclusions

The AS showed satisfactory feasibility, acceptability, scaling assumptions, internal consistency, and convergent validity. Responsiveness parameters were poor, probably due to the characteristics of the clinical study from which these data came. This trial is registered with NCT02289729.

Fatigue in Parkinson's disease: A systematic review and meta-analysis

We conducted a systematic review and meta-analysis aimed at establishing robust prevalence estimates and identifying clinical correlates of fatigue in PD. From 2,459 titles and abstracts, we selected 44 relevant studies (n = 7427 patients). Overall, the meta-analysis showed a prevalence of fatigue of 50% in PD. This prevalence estimate, however, was significantly moderated by study heterogeneity in measurement scales and cut-off thresholds. In contrast, demographic features, disease severity, cognitive impairment, and depression did not moderate prevalence estimates. Moreover, fatigue prevalence did not differ between de novo and treated PD patients. Compared to nonfatigued patients, fatigued patients had sligthly higher age (1.44 years), disease duration (0.93 years), l-dopa equivalent daily dose (50.89 units), UPDRS-III (4.99 points), and H & Y (0.33 points), as well as risk of comorbid depression (risk ratio = 1.89) and had a little lower MMSE score (-0.66 points). Fatigue was moderately associated with apathy (Hedges' g = 0.55), anxiety (Hedges' g = 0.67), daytime somnolence (Hedges' g = 0.43), sleep disturbances (Hedges' g = 0.66), and poorer quality of life (Hedges' g = 1.23). Our analyses suggest that fatigue is a frequent, independent nonmotor symptom in PD appearing early and persisting throughout the disease course, and that establishing uniform diagnostic criteria for PD-related fatigue is critical. In addition, several nonmotor symptoms appear to be associated with fatigue and negatively impact quality of life. Pharmacological and nonpharmacological interventions targeting fatigue and associated symptoms may improve quality of life in patients with PD. © 2018 International Parkinson and Movement Disorder Society.