mds-2026-parkinsons-sleep-circadian

MDS 2026 — Sleep and Circadian Disorders in Parkinson's Disease

Congress: Movement Disorder Society (MDS) International Congress 2026 Dates: October 4-8, 2026 Location: Seoul, Korea — COEX Convention and Exhibition Center Theme: Understanding Aging in Movement Disorders

Overview

MDS 2026 — Sleep and Circadian Disorders in Parkinson's Disease

Congress: Movement Disorder Society (MDS) International Congress 2026 Dates: October 4-8, 2026 Location: Seoul, Korea — COEX Convention and Exhibition Center Theme: Understanding Aging in Movement Disorders

Overview

Sleep and circadian disorders represent among the most prevalent and clinically significant non-motor manifestations in Parkinson's disease (PD), affecting up to 90% of patients. These disturbances often precede motor symptoms by years or decades and serve as critical prodromal biomarkers for synucleinopathies. MDS 2026 will highlight advances in understanding the pathophysiology of sleep-circadian dysfunction, biomarkers for phenoconversion prediction, and emerging therapeutic approaches for these often underrecognized symptoms.

The bidirectional relationship between sleep disruption and neurodegeneration creates a self-reinforcing cycle: while alpha-synuclein pathology damages brainstem and hypothalamic circuits governing sleep-wake regulation, impaired sleep accelerates pathological protein accumulation through glymphatic system dysfunction and circadian disruption. This mechanistic interplay positions sleep-circadian disorders as both early diagnostic markers and potential disease-modifying intervention targets.

REM Sleep Behavior Disorder (RBD)

Clinical Significance

REM Sleep Behavior Disorder (RBD) is the strongest prodromal marker for alpha-synucleinopathies, with over 80% of individuals with isolated RBD eventually developing Parkinson's disease, Dementia with Lewy Bodies, or Multiple System Atrophy[@iranzo2013][@hogl2018]. The disorder is characterized by loss of normal skeletal muscle atonia during REM sleep, resulting in dream-enactment behaviors ranging from limb movements to violent thrashing, punching, and kicking.

Key epidemiological features:

• Prevalence in PD: 30-50% of patients
• Annual phenoconversion rate: 6-8% per year
• 5-year cumulative rate: ~35-41%
• Lifetime risk: >90%

Pathophysiology

The neurodegenerative process underlying RBD involves:

This aligns with the Braak staging model, where alpha-synuclein pathology begins in the lower brainstem (Braak stages 1-2) before ascending to the substantia nigra (stage 3) and cortex (stages 4-6). RBD corresponds to early Braak stages, explaining why it often precedes motor symptoms by years to decades[@galbiati2025].

Biomarkers for Phenoconversion

Recent advances have improved prediction of which iRBD patients will convert to overt synucleinopathy[@miglis2021]:

| Biomarker Category | Markers | Predictive Value |
|-------------------|---------|------------------|
| Clinical | Quantitative motor testing, olfactory function, autonomic testing | Moderate |
| Neuroimaging | DAT imaging, MRI volumetrics, FDG-PET metabolic patterns | High |
| Fluid | Alpha-synuclein SAA, neurofilament light chain, glial fibrillary acidic protein | Very high |
| Electrophysiological | EEG slowing, event-related potentials | Moderate |

Alpha-Synuclein Seed Amplification Assays (SAA):
RT-QuIC and PMCA assays detect pathological alpha-synuclein in CSF with >90% sensitivity in iRBD patients, confirming the underlying synucleinopathy nature of the disorder.

Management

Pharmacological:

• Clonazepam: 0.25-2 mg at bedtime; first-line treatment effective in ~80% of patients
• Melatonin: 3-12 mg at bedtime; preferred in patients with contraindications to clonazepam

• Environmental safety measures (padding floor, removing sharp objects, bed rails)
• Sleep hygiene optimization

Insomnia and Sleep Fragmentation

Insomnia and sleep fragmentation affect the majority of PD patients, resulting from multiple converging mechanisms:

Contributing Factors

• Motor symptoms (tremor, rigidity, dyskinesias) disrupting sleep
• Nocturia
• Depression and anxiety
• Neurodegeneration of sleep-wake regulatory nuclei
• Dopaminergic medications

Types

• Sleep onset insomnia: Prolonged time to fall asleep
• Sleep maintenance insomnia: Frequent nighttime awakenings
• Early morning awakening: Premature waking with inability to return to sleep

Management Approaches

• Sleep hygiene optimization
• Cognitive behavioral therapy for insomnia (CBT-I)
• Melatonin supplementation
• Optimizing dopaminergic medication timing

Circadian Rhythm Disorders

Pathophysiology

Circadian dysfunction in PD arises from degeneration of multiple structures:

• Suprachiasmatic nucleus (SCN): The brain's master clock shows degeneration in PD
• Brainstem nuclei: Raphe nuclei, locus coeruleus, pedunculopontine nucleus
• Hypothalamic orexin neurons: Loss contributes to wakefulness instability

Clinical Manifestations

• Advanced sleep phase syndrome: Tendency to fall asleep and wake earlier
• Irregular sleep-wake pattern: Lack of consistent sleep schedule
• Reduced circadian amplitude: Weakened distinction between day and night
• Daytime sleepiness: Excessive somnolence not explained by nighttime sleep

Circadian Gene Expression

Recent research reveals circadian clock gene dysregulation in PD[@chen2025]:

Therapeutic Approaches

• Light therapy: Morning bright light exposure to strengthen circadian rhythms
• Melatonin supplementation: For circadian alignment
• Chronotherapy: Timing of activities to align circadian rhythms
• Exercise timing: Morning/afternoon activity preferred

Autonomic Dysfunction and Sleep

Autonomic dysfunction compounds sleep disturbances through multiple mechanisms:

Cardiovascular Contributions

• Orthostatic hypotension: Causes nighttime awakenings, sleep fragmentation
• Reduced heart rate variability: Impairs cardiovascular adaptation to sleep stages
• Blunted nocturnal blood pressure dipping: Disrupts normal sleep physiology

Thermoregulatory Dysfunction

• Abnormal core body temperature rhythms
• Reduced nighttime temperature drop (normal nocturnal dip absent)
• Impaired sweating responses affecting sleep comfort

Clinical Implications

Autonomic testing provides important prognostic information:

• Cardiac sympathetic denervation (reduced 123I-MIBG uptake) predicts faster phenoconversion
• Orthostatic hypotension correlates with disease severity and RBD presence

Sleep-Related Movement Disorders

Restless Legs Syndrome (RLS)

• Prevalence in PD: 10-20% of patients
• Features: Uncomfortable sensations in legs at rest, worsened in evening, relieved by movement
• Association: Often correlates with disease severity and dopaminergic medication use

Periodic Limb Movement Disorder (PLMD)

• Common comorbidity with RLS
• Can cause significant sleep fragmentation

Treatment

• Dopaminergic agents (pramipexole, ropinirole, rotigotine)
• Gabapentin, pregabalin for refractory cases

Excessive Daytime Sleepiness (EDS)

• Prevalence: Up to 50% of PD patients
• Contributing Factors:
• Dopaminergic medications
• Sleep fragmentation
• Neurodegeneration of wakefulness-promoting nuclei
• Obstructive sleep apnea

Assessment

• Epworth Sleepiness Scale
• Multiple Sleep Latency Test

Management

• Modafinil or methylphenidate (with caution)
• Treatment of underlying sleep apnea
• Sleep hygiene optimization

Actigraphy as Progression Marker

Recent studies demonstrate actigraphy utility for tracking PD progression through sleep-wake pattern analysis[@suzuki2025]:

| Measure | Utility |
|---------|---------|
| Sleep efficiency | Diagnostic and progression marker |
| Circadian amplitude | High for disease staging |
| Activity patterns | Very high for progression tracking |
| Rest-activity rhythms | Correlates with disease severity |

Emerging Research Directions

Neuroprotective Trials in RBD

The recognition of iRBD as a prodromal synucleinopathy has catalyzed neuroprotective intervention development:

• Anti-alpha-synuclein immunotherapy
• GLP-1 receptor agonists (semaglutide, exenatide)
• Exercise interventions
• Iron chelation therapy

Precision Medicine Approaches

Genotype-Phenotype Correlations:

• GBA carriers: Earlier onset, more severe autonomic dysfunction, faster phenoconversion
• LRRK2 carriers: Lower RBD prevalence, distinct progression pattern

• Motor-predominant (likely PD conversion)
• Cognitive-predominant (likely DLB conversion)
• Autonomic-predominant (likely MSA conversion)

Therapeutic Targets

• Alpha-synuclein reduction (antisense oligonucleotides, siRNA, CRISPR)
• Neuroinflammation modulation (TNF-alpha inhibitors, microglial modulators)
• Neurotrophic factor support (BDNF mimetics, GDNF delivery)
• Circadian clock gene targeting (REV-ERBα modulators)

Sessions and Presentations at MDS 2026

Expected Topics

Cross-Linking

• [MDS 2026 — Main Congress Page](/events/mds-2026)
• [MDS 2026 — Parkinson's Disease Sessions](/events/mds-2026-parkinsons-sessions)
• [MDS 2026 — Non-Motor Symptoms](/events/mds-2026-parkinsons-non-motor-symptoms)
• [Parkinson's Disease](/diseases/parkinsons-disease)
• [REM Sleep Behavior Disorder](/diseases/rem-sleep-behavior-disorder)
• [Sleep and Circadian Disruption in Neurodegeneration](/mechanisms/sleep-circadian-neurodegeneration)
• [Sleep Disorders in Neurodegeneration](/diseases/sleep-disorders-neurodegeneration)
• [Parkinson's Disease Autonomic Dysfunction](/diseases/parkinsons-autonomic-dysfunction)

References

External Links

• [MDS Congress 2026](https://www.mdscongress.org)
• [International Parkinson and Movement Disorders Society](https://www.movementdisorders.org/)
• [Parkinson's Foundation - Sleep Disorders](https://www.parkinson.org/)