Effects of Real vs. Soundless Acoustic Stimulation During Deep Sleep on Brain Activity, Memory, and Blood Biomarkers in Older Adults (60-85) With Mild Memory Impairment

University of Bern60 enrolled

Overview

This study aims to explore a non-invasive way to improve memory and slow cognitive decline in older adults by enhancing sleep quality. Dementia, a leading cause of death worldwide, is often associated with disturbed sleep, particularly the loss of deep, slow-wave sleep (SWS). SWS is important for memory and clearing waste from the brain. Poor SWS can worsen memory loss and allow harmful waste to build up, which may increase the risk of dementia. The investigators are testing whether phase-locked auditory stimulation (PLAS) can improve SWS in people at a mild stage of cognitive impairment. PLAS uses short sounds played at specific moments to strengthen slow-wave brain activity during sleep. The investigators previous laboratory based research has shown that this can improve memory and help with clearing waste from the brain. Now, the investigators want to test this in a real-world setting, over a longer period, which is unfeasible in a laboratory setting. In this study, 60 older adults will use home-use devices that deliver either real or sham (soundless) PLAS across two different 4-week periods. Memory will be tested using engaging "serious games." Before and after each experimental period, blood samples will be taken to measure dementia-related markers, and cognitive batteries will be performed. The investigators expect that PLAS will improve sleep, and that this will have a downstream effect on memory and brain clearance, potentially slowing the process of cognitive decline. If successful, this could lead to the development of an affordable treatment that helps people maintain brain health and prevent dementia.

Study Type

INTERVENTIONAL

Allocation

RANDOMIZED

Purpose

PREVENTION

Masking

SINGLE

Enrollment

Conditions

Interventions

Phase-locked auditory stimulation (PLAS)OTHER

Intervention: Verum Phase-Locked Auditory Stimulation (PLAS) Using the SleepLoop Device. The experimental intervention utilizes the SleepLoop device, a home-use, EEG-based system designed for phase-locked acoustic stimulation (PLAS). The device continuously monitors sleep through EEG (Fpz) alongside electrooculogram (EOG) and electromyogram (EMG) channels. The device employs a closed-loop algorithm that detects slow oscillations (SOs) in the EEG and delivers short sound stimuli (50 ms pink noise) during the positive half-waves of slow waves in slow-wave sleep (SWS). These stimuli are delivered through integrated headphones in the SleepLoop device. The intervention is applied during work days for 4 weeks. The algorithm is only active during SWS and does not deliver stimuli when the participant is awake, or in lighter sleep stages (N1, N2) or REM sleep. The intensity and algorithm sensitivity are individually calibrated for each participant to optimize stimulation.

Sham Phase-Locked Auditory StimulationOTHER

Participants will undergo the same procedure as the real Phase-Locked Auditory Stimulation (PLAS) intervention. However, during the sham condition, the headphones are turned off, and no auditory stimulation is delivered.

Eligibility

Sex: ALLMin age: 60 YearsMax age: 85 Years

Medical Language ↔ Plain English

Inclusion Criteria: * Written informed consent * Age between 60 and 85 years * Cognitive impairment (subjective and/or MoCA between 23-26) * Native German speakers or comparably fluent * Normal or corrected-to-normal vision. * Intact hearing * A close cohabitant (partner/sibling) should be present to support participants in using study materials/devices. Exclusion Criteria: * Insomnia assessed by the Regensburg Insomnia Scale (RIS; Crönlein et al., 2013) * Restless leg syndrome assessed by questions concerning typical symptoms. * Sleep apnoea assessed by the Berlin Questionnaire (BQ; Netzer et al., 1999) * Severely irregular sleep patterns assessed by the RIS and the Pittsburgh sleep quality index (PSQI; Buysse et al., 1989) * Symptoms of depression (Geriatric Depression Scale (GDS; Yesavage et al., 1982) ≥ 5) * History of untreated severe neurological and psychiatric diseases * Alcohol or substance abuse * Use of medication acting on the central nervous system

Outcomes

Primary Outcomes

Episodic memory performance differences (between and within subject) according to the experimental condition

Episodic memory performance will be assessed by means of serious games.

Time frame: Participants will play serious games on weekdays during the adaptation week, as well as on weekdays throughout both the first and second 4-week intervention periods.

Secondary Outcomes

Electrophysiological Response - Event-Related Potentials (ERPs)

Electrophysiological responses will be measured via EEG to assess event-related potentials (ERPs) in response to real versus sham acoustic stimulation.

Time frame: Sleep-Electrophysiology will be measured on weekdays during the adaptation week, as well as on weekdays throughout both the first and second 4-week intervention periods.

Electrophysiological Response - Power, Number, and Amplitude of Slow Oscillations (SO) and Spindles

Electrophysiological responses will be measured via EEG to assess the power, number, and amplitude of slow oscillations (SO) and sleep spindles in response to real versus sham acoustic stimulation.

Time frame: Sleep-electrophysiology will be measured on weekdays during the adaptation week, as well as on weekdays throughout both the first and second 4-week intervention periods.

Electrophysiological Response - Coupling of Slow Oscillations and Sleep Spindles

Electrophysiological responses will be measured via EEG to assess the coupling between slow oscillations and spindles in response to real versus sham acoustic stimulation.

Time frame: Sleep-electrophysiology will be measured on weekdays during the adaptation week, as well as on weekdays throughout both the first and second 4-week intervention periods.

Amyloid-Beta Response

Blood samples will be collected to measure plasma amyloid-beta levels and compare them across conditions.

Time frame: At baseline, after 4 weeks, after 6 weeks, after 10 weeks

Electrophysiology - Brain Age Estimation

EEG, EMG, and ECG will be used to estimate brain age and assess whether PLAS leads to a rejuvenation of the brain, reflecting a younger brain state. Machine learning will analyze sleep-EEG data to provide an accurate brain age estimate.

Time frame: Sleep electrophysiology will be measured on weekdays during the adaptation week and on weekdays throughout both the first and second 4-week intervention periods.