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This single-center study targets adults with distinct sleep profiles, divided into three categories: natural short sleepers, characterized by a reduced nocturnal sleep duration; subjects with idiopathic hypersomnia (IH) followed at the Sleep Disorders Unit of CHU Gui de Chauliac, with excessive daytime sleepiness; and control normal sleepers, with standard sleep duration and no specific complaints.
The aim of this study is to analyze the mechanisms of slow-wave regulation during sleep according to sleep phenotype (normal, short, and long sleepers/idiopathic hypersomnia) by examining the decay of EEG spectral power in the delta band over central regions during the first night of continuous 32-hour recording.
Sleep is a fundamental biological process essential for maintaining brain and systemic homeostasis, playing a key role in regulating cognitive, metabolic, and emotional functions. Over the past decades, numerous studies have shown that chronic sleep deprivation is associated with an increased risk of cardiovascular disease, diabetes, metabolic disorders, and cognitive deficits.
However, individuals differ in the amount of sleep they need for optimal functioning, suggesting inter-individual variability in homeostatic sleep regulation. Slow waves during sleep (0.5-4 Hz) are central to this regulation and closely reflect sleep pressure accumulated during wakefulness. During deep sleep, slow waves support the reorganization of neural connections, brain detoxification, and restoration of energy reserves. A reduction in slow-wave power, observed with aging or in pathological conditions, has been linked to reduced recovery capacity and increased cognitive vulnerability.
Sleep need is partly determined by genetics and varies between individuals. Approximately 5-7% of the population are short sleepers, able to maintain optimal cognitive and emotional performance despite sleeping ≤6 hours per night. Previous research suggests that short sleepers may compensate for shorter sleep by increasing sleep depth in the early phases, allowing faster recovery than hypersomnia patients.
At the other end of the spectrum is idiopathic hypersomnia (IH), a condition marked by excessive sleep need and persistent daytime sleepiness despite prolonged nocturnal sleep. Its pathophysiology remains poorly understood but may involve altered slow-wave regulation and impaired homeostatic sleep pressure.
The goal of this study is to compare slow-wave architecture among short sleepers, normal sleepers, and individuals with idiopathic hypersomnia to better understand inter-individual differences in sleep homeostasis. We hypothesize that delta power decay during the first night of recording will be faster and more pronounced in short sleepers, reflecting accelerated dissipation of sleep pressure, while it will be slower and less marked in IH patients, indicating impaired homeostatic regulation. This project will provide a detailed assessment of the neurophysiological mechanisms underlying differences in sleep profiles and their implications for health and cognitive functioning.
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| Label | Type | Description | Intervention Names |
|---|---|---|---|
| Short sleepers | Active Comparator | Average sleep duration < 6 hours per night |
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| Normal sleepers | Experimental | Sleep duration between 7 and 9 hours per night |
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| Long sleepers / Idiopathic Hypersomnia (IH) | Experimental | Presenting excessive daytime sleepiness, sleep duration > 9 hours per night |
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| Name | Type | Description | Arm Group Labels | Other Names |
|---|---|---|---|---|
| Actigraphy | Procedure | Actigraphy is a non-invasive method for measuring physical activity and sleep-wake cycles over an extended period, specifically two weeks in this protocol. It uses a small, portable device, the actigraph, which is often worn on the wrist of the non-dominant arm and continuously records the participant's movements. The data collected enables the estimation of periods of sleep and wakefulness, sleep quality, and circadian rhythms. |
| Measure | Description | Time Frame |
|---|---|---|
| The decrease in EEG spectral power in the delta band (0.5-4 Hz) over the central region during the first night of a continuous 32-hour recording. | The decay dynamics will be modeled using an exponential function. | Day 17 |
| Measure | Description | Time Frame |
|---|---|---|
| Changes in EEG spectral activity | Variation in EEG spectral power within the 0.5-9 Hz frequency range assessed across all channels of a 128-channel EEG system during the 30 minutes following awakening | Day 17 |
| 24-hour glycemic variability |
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Inclusion Criteria:
Weekday sleep duration ≤ 6 hours, with no significant increase at the weekend (weekend sleep duration ≤ 7 hours) and no complaints of daytime sleepiness (ESS <10).
-Normal sleepers: Weekday sleep duration of between 7 and 8 hours, with weekend sleep duration generally similar or slightly longer (between 7 and 9 hours), reflecting a normal sleep duration without restriction or significant catch-up sleep, and with no complaints of daytime sleepiness (ESS <10).
-HI subjects, with increased sleep duration: Increased sleep need, with a reported sleep duration of ≥ 10 hours per night and > 11 hours over a 24-hour period; increased sleep duration associated with excessive daytime sleepiness not explained by another sleep disorder.
Exclusion Criteria:
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| Name | Role | Phone | Extension | |
|---|---|---|---|---|
| Yves DAUVILLIERS, Pr | Contact | 04.67.33.63.61 | y-dauvilliers@chu-montpellier.fr |
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| Facility | Status | City | State | ZIP | Country | Contacts |
|---|---|---|---|---|---|---|
| Gui de Chauliac - CHU Montpellier | Montpellier | 34000 | France |
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| Polysomnographie (PSG 128) | Procedure | A video-polysomnography recording will be carried out to enable the scoring of the different stages of sleep and the analysis of the following parameters: - Electroencephalogram (EEG): A high-density cap (128 electrodes) will be fitted to record brain activity - Electromyogram (EMG): Three leads will be recorded at the chin. - Electrooculogram (EOG): Right and left eye movements will be recorded in phase opposition - Additional sensors will be fitted to record:
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| TILE test | Procedure | The modified TILE consists of five nap opportunities scheduled at 9 a.m., 11 a.m., 1 p.m., 3 p.m., and 5 p.m., during which participants are awakened after one minute of sleep to preserve the homeostatic process. Participants then undergo a modified TILE test, during which they are awakened each time they fall asleep. This allows for the measurement of sleep latency, defined as the time taken to fall asleep and the detection of abnormal REM sleep episodes. |
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| PVT | Procedure | The PVT is a standardised computer-based test lasting 5 minutes, used to assess sustained attention and psychomotor reactivity. At random intervals, a visual stimulus in the form of a digital stopwatch appears on the screen. The participant must then react as quickly as possible by pressing a button as soon as the stimulus appears, in order to stop the stopwatch. The test provides objective measures such as reaction time, the number of response omissions (lapses) and false alarms, offering a reliable indicator of alertness. |
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| Blood sample | Biological | The first blood sample will be collected during hospitalization to obtain serum for biobank establishment, and a second blood sample will be collected at the end of the protocol to obtain serum for biobank establishment. |
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| Freestyle Libre® senso | Procedure | The Abbott® FreeStyle Libre Pro iQ® is a continuous glucose monitoring system designed to measure interstitial glucose levels in real time in participants enrolled in clinical trials. This non-invasive, painless device is worn on the skin and continuously measures glucose concentrations in interstitial fluid, providing an accurate assessment of the glucose profile without the need for frequent blood sampling. The sensor will be fitted to provide continuous measurement of interstitial glucose levels |
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| Questionnaires | Behavioral | During their hospital stay, participants will complete a series of questionnaires designed to document sleepiness, daytime functioning, sleep quality, dietary and physical activity habits, and circadian rhythms: ESS, KSS, FOSQ, WPAI, IHSS, ISI, IPAQ, FFQ. Study of the chronobiological profile of participants, using the Morningness Eveningness Questionnaire (MEQ) by Horn and Östberg." |
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| Home EEG monitoring | Procedure | One week after hospitalization, sleep monitoring will be carried out at home using the Dreem® headband, a lightweight wearable EEG device designed to be worn during sleep. The headband features four electrodes positioned to measure brain activity in real time with high accuracy and connects wirelessly to a mobile application for easy data collection. It enables continuous recording of EEG signals, allowing identification of sleep stages as well as sleep microstructures such as spindles and slow waves. This recording will allow assessment of sleep quality in a natural environment and comparison of its characteristics with those observed in the laboratory. |
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| Bioelectrical impedance analysis | Procedure | Will be conducted to evaluate body composition, including fat mass, lean mass, and total body water. |
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will be assessed using continuous interstitial glucose monitoring with the FreeStyle Libre® system. Glucose values, expressed in mmol/L (or mg/dL), will be recorded at regular intervals and used to calculate variability metrics, including standard deviation (SD) and coefficient of variation (CV, %).
| Up to Day 18 |
| Lean mass index | Lean mass index will be assessed using Bioelectrical Impedance Analysis (BIA). | Up to Day 18 |
| Fat mass index | Fat mass index and fat mass index will be assessed using Bioelectrical Impedance Analysis (BIA). | Up to Day 18 |
| Physical activity level assessed using the International Physical Activity Questionnaire IPAQ | IPAQ is a seven-question self-report questionnaire that assesses physical activity over the past 7 days and provides a total score expressed in MET-minutes per week and/or categorical activity levels (low, moderate, high)." | Baseline visit (V1) |
| Food Frequency Questionnaire score | The Food Frequency Questionnaire (FFQ) is a self-administered tool used to assess habitual dietary intake over a defined period, providing a quantitative estimate of dietary intake." | Baseline visit (V1) |
| Epworth Sleepiness Scale (ESS) score | ESS is a short 8-item questionnaire designed to assess daytime sleepiness. Participants assign a score from 0 to 3 (0 = never; 1 = weak; 2 = moderate; 3 = strong).The minimum score is 0 and the maximum score is 24 | Baseline visit (V1) |
| Idiopathic hypersomnia severity scale (IHSS) score | IHSS is a tool used to measure the severity of the symptoms experienced by patients with IH during the previous month. The IHSS includes 2 items (1 and 2) on nighttime sleep duration and quality, 3 items (3, 4, and 5) on sleep inertia and sleep drunkenness after nighttime sleep and 1 (8) after daytime nap, and 3 items (6, 7, and 9) on diurnal symptoms (nap occurrence, daytime sleepiness). Items 10-14 assess daytime functioning alterations due to hypersomnolence. Six items are scored on a 3-point Likert scale and 8 items on a 4-point Likert scale; the Likert scale is a point scale that is used to allow the individual to express how much they agree or disagree with a particular statement. The total IHSS score is the sum of all item scores (range: 0-50), and higher scores indicate more severe symptoms | Baseline visit (V1) |
| Karolinska Sleepiness Scale (KSS) | KSS is a self-reported measure of subjective sleepiness at a specific time point. Participants rate their level of sleepiness over the preceding 10 minutes on a 9-point Likert scale ranging from 1 ('extremely alert') to 9 ('very sleepy, fighting sleep'). The KSS provides a measure of situational sleepiness, with higher scores indicating greater sleepiness | Baseline visit (V1) |
| The number of sleep-onset REM periods (SOREMPs) | corresponds to the total count of REM sleep episodes occurring within 15 minutes of sleep onset across all nap trials of the Multiple Sleep Latency Test (MSLT). Typically ranging from 0 to 5, this measure reflects abnormal REM intrusion when elevated and is a key diagnostic marker for conditions such as Narcolepsy, particularly when two or more SOREMPs are observed alongside reduced mean sleep latency | Up to Day 18 (During hospitalization) |
| Sleep latency at each test (minutes) | is the time from lights-off to the onset of sleep during each nap trial of the Multiple Sleep Latency Test (MSLT), typically conducted across 4 to 5 sessions. Shorter sleep latencies indicate greater daytime sleepiness, while longer latencies reflect higher alertness. This measure is commonly used, alongside SOREMP detection, to help diagnose conditions such as Narcolepsy and excessive daytime sleepiness | Up to Day 18 (During hospitalization) |
| Mean sleep latency is the average time (in minutes) | it takes a participant to fall asleep across all nap trials of the Multiple Sleep Latency Test (MSLT). It is calculated by averaging the sleep latency values from each nap session (typically 4 to 5 tests). Lower mean sleep latency indicates greater daytime sleepiness, while higher values reflect better alertness. This parameter is a key diagnostic indicator, particularly for conditions such as Narcolepsy and excessive daytime sleepiness | Up to Day 18 (During hospitalization) |
| Presence of a sleep-onset REM periods (SOREMP) | refers to whether REM sleep occurs within 15 minutes after sleep onset during each nap trial of the Multiple Sleep Latency Test (MSLT). This measure is recorded as a binary outcome for each test (present = 1, absent = 0) and reflects abnormal REM intrusion when present. It is used alongside sleep latency to help identify sleep disorders such as Narcolepsy and excessive daytime sleepiness | Up to Day 18 (During hospitalization) |
| Questionnaire on Functional Outcomes of Sleep | FOSQ : a self-administered instrument consisting of 10 items evaluating the impact of sleepiness and fatigue on daily activities. Each item is rated on a 4- to 6-point Likert scale according to the frequency or degree of difficulty experienced, with higher scores indicating better functional status | Baseline visit (V1) |
| Work Productivity and Activity Impairment- General Health (WPAI:GH) | WPAI:GH is a well validated instrument to measure the effect of health conditions on work productivity and daily activities. The WPAI-GH consists of six questions: 1 = currently employed; 2 = hours missed due to health problems; 3 = hours missed other reasons; 4 = hours actually worked; 5 = degree health affected productivity while working (using a 0 to 10 Visual Analogue Scale (VAS)); 6 = degree health affected productivity in regular unpaid activities (VAS). | Baseline visit (V1) |
| Sleepiness severity scores on the Insomnia Severity Index (ISI) | The Insomnia Severity Index (ISI) is a 7-item self-report questionnaire assessing the nature, severity of both nighttime and daytime components of insomnia, and impact of insomnia. Each item is scored 0 (no problem) - 4 (very big problem) with total between 0-28 (absence of insomnia (0-7); sub-threshold insomnia (8-14); moderate insomnia (15-21); and severe insomnia (22-28) | Baseline visit (V1) |
| Morningness-Eveningness Questionnaire (MEQ) score | MEQ : a validated self-reported instrument evaluating individual chronotype. The MEQ provides a total score classifying participants along a continuum from eveningness to morningness, with higher scores indicating a stronger morning-type preference | Baseline visit (V1) |
| Psychomotor vigilance task (PVT) | PVT is a widely utilized as a measure of behavioral alertness, primary due to its high sensitivity to sleep deprivation and its psychometric advantages over other cognitive tests. The standard 10-min PVT measures sustained or vigilant attention by recording response times (RT) to visual (or auditory) stimuli presented at random inter-stimulus intervals | Up to Day 18 (During hospitalization) |
| Serum protein levels | Serum proteins will be collected for future exploratory analyses using the NULISA platform | Up to Day 18 (During hospitalization) |
| ID | Term |
|---|---|
| D000077260 | Sleepiness |
| ID | Term |
|---|---|
| D012816 | Signs and Symptoms |
| D013568 | Pathological Conditions, Signs and Symptoms |
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| ID | Term |
|---|---|
| D056044 | Actigraphy |
| D001800 | Blood Specimen Collection |
| D011795 | Surveys and Questionnaires |
| ID | Term |
|---|---|
| D008991 | Monitoring, Physiologic |
| D019937 | Diagnostic Techniques and Procedures |
| D003933 | Diagnosis |
| D061725 | Accelerometry |
| D008919 | Investigative Techniques |
| D013048 | Specimen Handling |
| D019411 | Clinical Laboratory Techniques |
| D011677 | Punctures |
| D013514 | Surgical Procedures, Operative |
| D003625 | Data Collection |
| D004812 | Epidemiologic Methods |
| D017531 | Health Care Evaluation Mechanisms |
| D011787 | Quality of Health Care |
| D017530 | Health Care Quality, Access, and Evaluation |
| D011634 | Public Health |
| D004778 | Environment and Public Health |
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