Auditory Sleep Stimulation or Sham in People With Parkinson Disease Mild Cognitive Impairment During Cognitive Training

Parkinson's disease (PD) is a progressive neurodegenerative disorder associated not only with motor symptoms (such as tremor, slowness of movement, and rigidity), but also with a broad range of non-motor symptoms. Sleep disturbances are common, and many individuals with PD develop cognitive impairment, ranging from mild cognitive impairment (MCI) to dementia. For early cognitive impairment in PD, pharmacological treatment options are limited, and there are currently no established therapies that reliably prevent further cognitive decline. There is therefore a clear need to develop and evaluate non-pharmacological interventions that can support cognitive functioning in this population.

Cognitive training (CogT) is a structured, exercise-based intervention targeting cognitive domains such as attention, memory, and executive functions (e.g., planning and coordination of actions). Evidence supports the efficacy of CogT in PD and in older adults; however, response to training varies considerably between individuals. Sleep-particularly deep sleep-has been proposed as an important factor influencing learning and cognitive performance. Deep sleep is implicated in processes relevant to memory consolidation and daytime cognition. Because sleep disturbances are frequent in PD, impaired sleep may represent a barrier to achieving optimal benefits from CogT.

This study evaluates whether enhancing deep sleep using phase-targeted auditory stimulation (PTAS) can improve the effectiveness of CogT in people with PD and MCI. PTAS is a non-pharmacological method that delivers soft, non-arousing sounds during sleep with the aim of supporting deep sleep. The intervention is administered using a wearable headband device developed at the University of Zurich and ETH Zurich. The device is designed for home use and can be worn during sleep in the participant's own bed. The technology has been used in previous research in younger and older healthy individuals as well as in people with PD, with no relevant side effects reported, and has demonstrated beneficial effects on measures of deep sleep.

Study Design

This is a double-blind, randomized, sham-controlled trial. After eligibility screening, participants are randomly assigned to one of two groups:

Active auditory stimulation group: Participants complete digital CogT and use the headband during sleep with active PTAS intended to enhance deep sleep.

Sham stimulation group: Participants complete the same digital CogT and use the headband during sleep, but the sounds delivered do not provide targeted deep sleep stimulation (sham condition).

Neither participants nor study staff involved in assessments and trial conduct are aware of group allocation.

Study Procedures The intervention phase lasts 5 weeks and is performed primarily at home. Participants use the headband during sleep as often as possible throughout the 5-week period. Digital CogT is performed at home on a tablet during weeks 2-5 (total of 4 weeks), three sessions per week, approximately 50 minutes per session, with scheduling adapted to individual daily routines.

Participants attend study visits at University Hospital Zurich, including assessments before the intervention, after the 5-week intervention, and at a 3-month follow-up. These visits include approximately half a day of assessments and an overnight stay in the sleep laboratory. Assessments include standardized neuropsychological testing of cognitive performance, questionnaires addressing sleep-related symptoms, non-motor symptoms, and quality of life, and overnight recording of brain activity during sleep using high-density electroencephalography (hdEEG). Blood samples are collected to explore biomarkers that may reflect biological processes related to brain function. In addition, participants wear an actimeter (a watch-like activity monitor) for defined periods to capture activity patterns and sleep-wake behavior.

Prior to final enrollment, participants complete a familiarization phase at home (typically 1-5 nights) to assess tolerability of sleeping with the headband. Depending on prior clinical information, a one-night home sleep assessment may be performed to screen for relevant sleep disorders such as sleep apnea.

Outcome and Objectives - Overview The primary objective is to determine whether enhancement of deep sleep via PTAS increases the benefit of CogT on cognitive performance in people with PD and MCI. Secondary objectives include evaluating the effects of the combined intervention on sleep physiology (as assessed by hdEEG) and exploratory blood-based biomarkers.

The study is conducted in Switzerland in accordance with applicable legal and ethical requirements for research involving humans, including data protection regulations, and has been reviewed and authorized by the responsible ethics committee and Swissmedic. The study is planned as a national trial in Switzerland with approximately 50 participants. Participant data and samples are coded to protect confidentiality, and participation is voluntary; participants may withdraw at any time without consequences for their ongoing medical care.