This study tests the efficacy of cognitive behavioural therapy for insomnia (CBT-I) with or without adjunct melatonin in older adults with insomnia. Adults aged 60 or above with chronic insomnia will be randomly assigned to one of three groups: (1) CBT-I plus nightly melatonin, (2) CBT-I plus nightly placebo tablet, or (3) sleep health psychoeducation plus nightly placebo tablet. All group sessions occur weekly for four weeks.
This randomized, double-blind, placebo-controlled trial examines whether cognitive behavioural therapy for insomnia (CBT-I) with or without adjunct melatonin improves sleep and circadian outcomes as well as daytime functioning in older adults with chronic insomnia. Eligible participants (aged ≥60 years, meeting DSM-5 criteria for insomnia disorder) will be recruited and randomly assigned to one of the three parallel groups: (1) CBT-I combined with nightly melatonin, (2) CBT-I with nightly placebo, or (3) sleep-health psychoeducation with nightly placebo. All interventions involve four weekly 90-minute group sessions (6-8 participants per group) conducted in person. Melatonin (3 mg immediate-release) or a matched placebo will be taken 30 minutes before habitual bedtime for four weeks. Assessments will be conducted at baseline, mid-treatment (week 2, for the primary outcome only), and post-treatment (week 4) for all participants, and additionally at three-month and six-month follow-ups for participants in the two CBT-I groups. Data collection includes validated questionnaires on sleep, circadian, mood, fatigue, and quality of life, as well as computerized cognitive tasks to assess domains such as attention, working memory, and executive function. Objective sleep and circadian parameters will be measured by actigraphy for seven consecutive nights, along with a daily sleep diary. Participants will also complete polysomnography (PSG) for objective sleep assessment. To index circadian timing, a subset of participants will collect saliva samples (about 1 mL each) every 30 minutes under dim-light conditions in the evening to estimate dim-light melatonin onset (DLMO). The primary outcome is the change in self-reported insomnia severity from baseline to post-treatment. Secondary outcomes include resumption and treatment response of insomnia, clinical symptom severity, objective and subjective sleep- and circadian-related outcomes, mood, daytime functioning, quality of life, and cognitive performance. The study is conducted across two sites - The University of Hong Kong (Department of Psychology) and The Chinese University of Hong Kong (Department of Psychiatry). Findings are expected to clarify whether melatonin can augment the efficacy and sustainability of CBT-I in older adults, providing new insights into circadian-based strategies for improving sleep health in late life.
CBT-I is a multi-component, non-pharmacologic intervention that targets behavioural, cognitive, and physiological perpetuating factors of insomnia. Four group-based weekly sessions (120-min; 6-8 participants) will be delivered. Components: sleep psychoeducation, sleep hygiene, stimulus control, sleep restriction, relaxation training, cognitive restructuring (addressing dysfunctional beliefs about sleep), and relapse prevention. Delivered in-person by trained therapists supervised weekly by the PI.
Melatonin is a safe and accessible sleep-promoting supplement. The tablet will be taken once daily, 30 minutes before habitual bedtime for 4 weeks, concurrent with CBT-I.
Sleep Research Clinic and Laboratory, Department of Psychology, The University of Hong Kong
Hong Kong, Hong Kong
RECRUITINGInsomnia Symptoms - Insomnia Severity Index
Insomnia symptoms measured by Insomnia Severity Index (ISI). ISI is a 5-item self-rated scale. Possible scores range from 0 to 20, with higher scores indicating greater insomnia severity.
Time frame: Baseline, Mid-session (Week 2 of the intervention), Post-Treatment (one-week after treatment conclusion) for all participants, and at Post-Treatment 3-month and Post-Treatment 6-month for participants in the treatment groups.
Treatment Response of Insomnia
Defined as a decrease of ≥ 8 points on the ISI (self-reported)
Time frame: Post-Treatment (one-week after treatment conclusion) for all participants, and at Post-Treatment 3-month and Post-Treatment 6-month for participants in the treatment groups.
Remission of insomnia
Insomnia remission is defined as an ISI score less than 8. The outcome will be reported as the number and percentage of participants meeting remission criteria.
Time frame: Post-Treatment (one-week after treatment conclusion) for all participants, and at Post-Treatment 3-month and Post-Treatment 6-month for participants in the treatment groups.
Self Report Sleep Quality - The Pittsburgh Sleep Quality Index
Pittsburgh Sleep Quality Index (PSQI) is a self-rated scale consisting of 19 questions. All items are combined to form seven component scores on different aspects of sleep quality, each of which ranges from 0 to 3 points with higher scores representing more sleep disturbance. The seven component scores are added to one global score, which ranges from 0 to 21, with higher scores indicating more difficulties with sleep.
Time frame: Baseline, Post-Treatment (one-week after treatment conclusion) for all participants, and at Post-Treatment 3-month and Post-Treatment 6-month for participants in the treatment groups.
Self-Report Chronotype Measures The Munich Chronotype Questionnaire
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Study Type
INTERVENTIONAL
Allocation
RANDOMIZED
Purpose
TREATMENT
Masking
DOUBLE
Enrollment
183
Four group-based weekly sessions covering sleep hygiene, healthy diet, and exercise habits for older adults. This arm will not include any active therapeutic CBT-I components. It serves as the active control, controlling for attention and non-specific expectancy effects.
Placebo capsule identical in appearance to the melatonin capsule, taken once daily, 30 minutes before habitual bedtime for 4 weeks. Used in CBT-I + Placebo and Psychoeducation + Placebo arms.
The Munich Chronotype Questionnaire (MCTQ) is a self-report measures of sleeping patterns during weekdays and weekends separately. The Mid-Sleep Time (MSF/MSFsc) are used to as an indicator of chronotype, where individuals with earlier mid-sleep time reflect a morning chronotype and later mid-sleep time reflect an evening chronotype.
Time frame: Baseline, Post-Treatment (one-week after treatment conclusion) for all participants, and at Post-Treatment 3-month and Post-Treatment 6-month for participants in the treatment groups.
Self-Report Chronotype Preference: The Morningness-Eveningness Questionnaire
The Morningness-Eveningness Questionnaire (MEQ) is a 19-item self-assessment tool used to determine an individual's chronotype with a total score between 16 and 86. A higher score indicates a morning chronotype (e.g., "morning type"), a lower score indicates an evening chronotype (e.g., "evening type"), and a mid-range score indicates an intermediate chronotype.
Time frame: Baseline, Post-Treatment (one-week after treatment conclusion) for all participants, and at Post-Treatment 3-month and Post-Treatment 6-month for participants in the treatment groups.
Self-report Mood Symptoms - Hospital Anxiety and Depression Scale
Hospital Anxiety and Depression Scale (HADS), a 14-item self-report questionnaire used to screen for anxiety and depression in a patient's recent past week. The depression subscale ranges in scores from 0 to 21, with higher scores indicating more severe states of depression. Similarly, the anxiety subscale ranges in scores from 0-21 with higher scores indicating more severe states of anxiety.
Time frame: Baseline, Post-Treatment (one-week after treatment conclusion) for all participants, and at Post-Treatment 3-month and Post-Treatment 6-month for participants in the treatment groups.
Self-report Daytime Sleepiness - Epworth Sleepiness Scale
Epworth sleepiness scale, a short self-assessment to identify how likely you are to fall asleep during the daytime. Scores range from 0 to 24, a higher score indicates a higher level of excessive daytime sleepiness.
Time frame: Baseline, Post-Treatment (one-week after treatment conclusion) for all participants, and at Post-Treatment 3-month and Post-Treatment 6-month for participants in the treatment groups.
Self-report Daytime Fatigue - Multidimensional Fatigue Inventory
Multidimensional Fatigue Inventory (MFI) is a 20-item self-rated scale on fatigue symptoms. There are three subscales, measuring the physical (possibly scored from 7 to 35), mental (possibly scored from 6 to 30), and spiritual (possibly scored from 7 to 35), dimensions of fatigue. A grand total score can be calculated by summing up the three sub scores. In all cases, a higher score represents higher fatigue symptoms.
Time frame: Baseline, Post-Treatment (one-week after treatment conclusion) for all participants, and at Post-Treatment 3-month and Post-Treatment 6-month for participants in the treatment groups.
Overall Severity of Clinical Symptoms
Clinical Global Impression (CGI) Scale is a clinician-rated scale, comprised of two one-item subscales: Severity of Illness (CGI-S) subscale evaluating the severity of psychopathology, and Clinical Global Improvement Scale (CGI-I) evaluating change from the initiation of treatment. In both cases, the score is given on a seven-point scale, with higher values indicating higher severity of illness and larger improvement, respectively. CGI-S will be used to evaluate the overall severity of clinical symptoms.
Time frame: Baseline, Post-Treatment (one-week after treatment conclusion) for all participants, and at Post-Treatment 3-month and Post-Treatment 6-month for participants in the treatment groups.
Overall Treatment Response
Clinical Global Impression (CGI) Scale is a clinician-rated scale, comprised of two one-item subscales: Severity of Illness (CGI-S) subscale evaluating the severity of psychopathology, and Clinical Global Improvement Scale (CGI-I) evaluating change from the initiation of treatment. In both cases, the score is given on a seven-point scale, with higher values indicating higher severity of illness and larger improvement respectively. Overall treatment response is defined as CGI-I \<3 (clinician-rated)
Time frame: Post-Treatment (one-week after treatment conclusion) for all participants, and at Post-Treatment 3-month and Post-Treatment 6-month for participants in the treatment groups.
Self Report Quality of Life - 36-Item Short Form Health Survey
The SF-36, or Short Form 36 Health Survey, is a 36-item patient-reported questionnaire that measures health status and quality of life. It assesses eight different health domains, including physical functioning, bodily pain, vitality, general health, role-physical, role-emotional, social functioning, and mental health. Total scores range from 0 to 100, where higher scores indicate better health.
Time frame: Baseline, Post-Treatment (one-week after treatment conclusion) for all participants, and at Post-Treatment 3-month and Post-Treatment 6-month for participants in the treatment groups.
Objective Cognitive Performance (attention/inhibitory ability)
The stop-signal task is a behavioural task that measures a person's ability to inhibit a pre-programmed response. The main measure of inhibitory control is the stop-signal reaction time (SSRT), which estimates the time it takes to cancel a response. A longer SSRT indicates a slower ability to inhibit a response.
Time frame: Baseline, Post-Treatment (one-week after treatment conclusion) for all participants, and at Post-Treatment 3-month and Post-Treatment 6-month for participants in the treatment groups.
Objective Cognitive Performance (Alertness)
Psychomotor Vigilance Task (PVT) is a reaction-time test that measures sustained attention by having a person respond as quickly as possible to a visual stimulus that appears at random intervals. Reaction Time (RT): The primary measurement is how quickly the participant responds to the stimulus. Lapses: A lapse is a failure to respond to the stimulus within a certain time frame, often defined as a reaction time longer than 500 milliseconds.
Time frame: Baseline, Post-Treatment (one-week after treatment conclusion) for all participants, and at Post-Treatment 3-month and Post-Treatment 6-month for participants in the treatment groups.
Objective Cognitive Performance (working memory by N-Back)
N-back Task for assessing working memory capacity and manipulation. In N-back Task, a d prime score will be calculated based on the signal detection theory, where a higher score indicates better working memory performance.
Time frame: Baseline, Post-Treatment (one-week after treatment conclusion) for all participants, and at Post-Treatment 3-month and Post-Treatment 6-month for participants in the treatment groups.
Objective Cognitive Performance (problem solving)
Wisconsin Card Sorting Test for assessing problem solving. In Wisconsin Card Sorting Test, lower executive functioning is indicated by a higher percentage of persistent errors and a higher number of trials taken to complete the first category.
Time frame: Baseline, Post-Treatment (one-week after treatment conclusion) for all participants, and at Post-Treatment 3-month and Post-Treatment 6-month for participants in the treatment groups.
Objective Cognitive Performance (episodic memory)
Chinese Auditory Verbal Learning Task for assessing episodic memory, where a higher number of recalled words indicates better episodic memory performance.
Time frame: Baseline, Post-Treatment (one-week after treatment conclusion) for all participants, and at Post-Treatment 3-month and Post-Treatment 6-month for participants in the treatment groups.
Self-report Cognition - Multifactorial Memory Questionnaire
Multifactorial Memory Questionnaire (MMQ) is a 57-item self-report assessing memory satisfaction, ability and strategy use (three subscales).For each subscale, score ranges: for each subscale: Satisfaction (0-72), Ability (0-80), and Strategy (0-76). A higher score generally indicates better self-reported memory functioning, higher satisfaction with memory, and greater use of memory strategie
Time frame: Baseline, Post-Treatment (one-week after treatment conclusion) for all participants, and at Post-Treatment 3-month and Post-Treatment 6-month for participants in the treatment groups.
Self-report Depressive Symptoms - Beck Depression Inventory-II
Beck Depression Inventory-II (BDI-II) is 21-item self-report of depressive-symptom severity during the past two weeks (0-63). Higher scores indicate more severe depressive symptoms
Time frame: Baseline, Post-Treatment (one-week after treatment conclusion) for all participants, and at Post-Treatment 3-month and Post-Treatment 6-month for participants in the treatment groups.
Clinician Rated Depressive Symptoms - The Hamilton Rating Scale for Depression
The Hamilton Rating Scale for Depression (HAM-D17) is a 17-item interview to assess the severity of depression symptoms. Scores are interpreted based on a range: 0-7 indicates no depression, 8-16 is mild, 17-23 is moderate, and 24 or higher is severe depression.
Time frame: Baseline, Post-Treatment (one-week after treatment conclusion) for all participants, and at Post-Treatment 3-month and Post-Treatment 6-month for participants in the treatment groups.
Self Report: Dysfunctional sleep beliefs
Dysfunctional Beliefs and Attitudes about Sleep Scale (DBAS): 16 statements evaluating maladaptive sleep-related cognitions (0-160). A higher score indicates a higher level of dysfunctional, unhelpful, or rigid beliefs about sleep.
Time frame: Baseline, Post-Treatment (one-week after treatment conclusion) for all participants, and at Post-Treatment 3-month and Post-Treatment 6-month for participants in the treatment groups.
Self-report Cognitive Functioning: Cognitive Failures Questionnaire Score
Cognitive Failures Questionnaire; 25 items indexing self-reported failures in attention, memory and action execution, 0-100. Indicates a higher frequency of everyday cognitive failures.
Time frame: Baseline, Post-Treatment (one-week after treatment conclusion) for all participants, and at Post-Treatment 3-month and Post-Treatment 6-month for participants in the treatment groups.
Self Report: Pre-sleep somatic arousal
Pre-Sleep Arousal Scale (PSAS): 16 items measuring somatic and cognitive arousal at bedtime (8 each; 1-5 Likert, total score range 8-40). Higher scores indicate greater pre-sleep physical distress.
Time frame: Baseline, Post-Treatment (one-week after treatment conclusion) for all participants, and at Post-Treatment 3-month and Post-Treatment 6-month for participants in the treatment groups.
Self Report: Stress-related insomnia vulnerability
Ford Insomnia Response to Stress Test (FIRST): 9-item trait measure of likelihood that stress will provoke insomnia (0-36).
Time frame: Baseline, Post-Treatment (one-week after treatment conclusion) for all participants, and at Post-Treatment 3-month and Post-Treatment 6-month for participants in the treatment groups.
Self Report: Sleep Hygiene Practices Scale (SHPS)
Sleep Hygiene Practices Scale (SHPS): 30 items assessing frequency of behaviours affecting sleep quality (0-120). Higher scores indicate more maladaptive (unhealthier) sleep hygiene practices
Time frame: Baseline, Post-Treatment (one-week after treatment conclusion) for all participants, and at Post-Treatment 3-month and Post-Treatment 6-month for participants in the treatment groups.
Sleep Diary Measure - Time in Bed (TIB)
Daily sleep diary for consecutive seven days. Sleep parameter estimated by daily sleep diary: time in bed (TIB) in hours
Time frame: Baseline, Post-Treatment (one-week after treatment conclusion) for all participants, and at Post-Treatment 3-month and Post-Treatment 6-month for participants in the treatment groups.
Sleep Diary Measure - Total Sleep Time (TST)
Daily sleep diary for consecutive seven days. Sleep parameter estimated by daily sleep diary: total sleep time (TST) in hours
Time frame: Baseline, Post-Treatment (one-week after treatment conclusion) for all participants, and at Post-Treatment 3-month and Post-Treatment 6-month for participants in the treatment groups.
Sleep Diary Measure - Sleep Onset Latency (SOL)
Daily sleep diary for consecutive seven days. Sleep parameter estimated by daily sleep diary: sleep onset latency (SOL) in mins
Time frame: Baseline, Post-Treatment (one-week after treatment conclusion) for all participants, and at Post-Treatment 3-month and Post-Treatment 6-month for participants in the treatment groups.
Sleep Diary Measure - Wake After Sleep Onset (WASO)
Daily sleep diary for consecutive seven days. Sleep parameter estimated by daily sleep diary: wake after sleep onset (WASO) in mins
Time frame: Baseline, Post-Treatment (one-week after treatment conclusion) for all participants, and at Post-Treatment 3-month and Post-Treatment 6-month for participants in the treatment groups.
Sleep Diary Measure - Sleep Efficiency (SE)
Daily sleep diary for consecutive seven days. Sleep parameter estimated by daily sleep diary: sleep efficiency (SE), which is calculated by total sleep time divided by total time in bed, %
Time frame: Baseline, Post-Treatment (one-week after treatment conclusion) for all participants, and at Post-Treatment 3-month and Post-Treatment 6-month for participants in the treatment groups.
Objective Actigraphy - Time in Bed (TIB)
The duration of time spent in bed attempting to sleep, estimated from 7-night wrist actigraphy. Reported as mean minutes per night across the recording period.
Time frame: Baseline, Post-Treatment (one-week after treatment conclusion) for all participants, and at Post-Treatment 3-month and Post-Treatment 6-month for participants in the treatment groups.
Objective Actigraphy - Total Sleep Time (TST)
The total amount of sleep obtained during a sleep period, estimated from 7-night wrist actigraphy. Reported as mean minutes per night across the recording period.
Time frame: Baseline, Post-Treatment (one-week after treatment conclusion) for all participants, and at Post-Treatment 3-month and Post-Treatment 6-month for participants in the treatment groups.
Objective Actigraphy - Sleep Onset Latency (SOL)
The amount of time it takes to fall asleep after attempting to do so, estimated from 7-night wrist actigraphy. Reported as mean minutes per night across the recording period.
Time frame: Baseline, Post-Treatment (one-week after treatment conclusion) for all participants, and at Post-Treatment 3-month and Post-Treatment 6-month for participants in the treatment groups.
Objective Actigraphy - Wake After Sleep Onset (WASO)
The amount of time spent awake after initially falling asleep, estimated from 7-night wrist actigraphy. Reported as mean minutes per night across the recording period.
Time frame: Baseline, Post-Treatment (one-week after treatment conclusion) for all participants, and at Post-Treatment 3-month and Post-Treatment 6-month for participants in the treatment groups.
Objective Actigraphy - Sleep Midpoint Variability
The standard deviation of the sleep midpoint, defined as (sleep onset + sleep offset) / 2, across the 7-night recording. Higher values reflect more irregular sleep timing across nights.
Time frame: Baseline, Post-Treatment (one-week after treatment conclusion) for all participants, and at Post-Treatment 3-month and Post-Treatment 6-month for participants in the treatment groups.
Objective Actigraphy - Sleep Efficiency (SE)
The percentage of time spent asleep while in bed, calculated as (TST / TIB) × 100, estimated from 7-night wrist actigraphy.
Time frame: Baseline, Post-Treatment (one-week after treatment conclusion) for all participants, and at Post-Treatment 3-month and Post-Treatment 6-month for participants in the treatment groups.
Objective Actigraphy - Acrophase
The clock time of maximum activity estimated from a cosinor model fitted to the 7-day rest-activity record. Represents the timing of peak daily activity.
Time frame: Baseline, Post-Treatment (one-week after treatment conclusion) for all participants, and at Post-Treatment 3-month and Post-Treatment 6-month for participants in the treatment groups.
Objective Actigraphy - Amplitude
The difference between the peak and nadir of the cosinor-fitted rest-activity curve across the 7-day recording. Reflects the overall strength of the circadian rest-activity rhythm.
Time frame: Baseline, Post-Treatment (one-week after treatment conclusion) for all participants, and at Post-Treatment 3-month and Post-Treatment 6-month for participants in the treatment groups.
Objective Actigraphy - Intradaily Variability (IV)
An index ranging from 0 to 2 quantifying the degree of rest-activity rhythm fragmentation. Higher values reflect greater fragmentation, indicating more daytime napping or nocturnal awakening.
Time frame: Baseline, Post-Treatment (one-week after treatment conclusion) for all participants, and at Post-Treatment 3-month and Post-Treatment 6-month for participants in the treatment groups.
Objective Actigraphy - Interdaily Stability (IS)
An index ranging from 0 to 1 reflecting the synchronisation of the rest-activity rhythm to the 24-hour light-dark cycle. Higher values reflect stronger synchronisation.
Time frame: Baseline, Post-Treatment (one-week after treatment conclusion) for all participants, and at Post-Treatment 3-month and Post-Treatment 6-month for participants in the treatment groups.
Objective Actigraphy - L5
The clock time of onset of the 5 least active consecutive hours across the 7-day recording, presumed to represent the habitual sleep window.
Time frame: Baseline, Post-Treatment (one-week after treatment conclusion) for all participants, and at Post-Treatment 3-month and Post-Treatment 6-month for participants in the treatment groups.
Objective Actigraphy - M10
Actigraphic assessment for consecutive seven days. Circadian parameters computed by the nonparametric circadian rhythm analysis method - start times and average activity of M10 (i.e. 10 h with maximal activity).
Time frame: Baseline, Post-Treatment (one-week after treatment conclusion) for all participants, and at Post-Treatment 3-month and Post-Treatment 6-month for participants in the treatment groups.
Objective Actigraphy - Fluctuation of the midpoint of sleep
Actigraphic assessment for seven consecutive days. The standard deviation of the midpoint of sleep will be derived from actigraphy, defined as sleep onset + sleep offset) / 2, across the 7-night recording.
Time frame: Baseline, Post-Treatment (one-week after treatment conclusion) for all participants, and at Post-Treatment 3-month and Post-Treatment 6-month for participants in the treatment groups.
Objective Circadian Measures: Dim-Light Melatonin Onset (DLMO) - Sleep Onset Phase angle
DLMO time to sleep-onset phase angle: Interval (min) from DLMO time to diary-determined sleep-onset time. Sleep-onset time will be calculated as the mean sleep-onset time across valid diary nights.
Time frame: Baseline and Post-Treatment (one-week after treatment conclusion)
Objective Circadian Measures: Dim-Light Melatonin Onset (DLMO) - DLMO Timing
Dim-light melatonin onset (express as time value hh:mm) is determined by 6-hours salivary melatonin collected at 30-minutes interval. Melatonin is assayed by gas chromatography-mass spectrometry. DLMO time: Clock time (hh:mm) at which salivary melatonin first exceeds the 3 pg mL-¹ threshold under \< 10 lux illumination.
Time frame: Baseline and Post-Treatment (one-week after treatment conclusion)
Objective Circadian Measures: Dim-Light Melatonin Onset (DLMO) - Sleep Midpoint Phase Angel
DLMO time to sleep-midpoint phase angle is the initerval (min) from DLMO time to diary-determined sleep midpoint. Sleep midpoint will be calculated as halfway between sleep onset and final sleep offset/waketime.
Time frame: Baseline and Post-Treatment (one-week after treatment conclusion)
Dim Light Melatonin Onset - Lights-Off Phase Angel
Interval (min) from DLMO time to diary-determined lights-off/bedtime; indexing the timing of attempted sleep relative to biological night onset. Lights-off/bedtime will be calculated as the mean diary-reported lights-off/bedtime across valid diary nights.
Time frame: Baseline and Post-Treatment (one-week after treatment conclusion)
Pupil Light Reflex - T75 Recovery Time
T75 recovery time is the seconds from stimulus offset to 75% return toward baseline pupil diameter, reflecting the post-illumination pupil response (PIPR), a melanopsin-mediated circadian biomarker.
Time frame: Baseline, Post-Treatment (one-week after treatment conclusion) for all participants, and at Post-Treatment 3-month and Post-Treatment 6-month for participants in the treatment groups.
Polysomnography - Time in Bed
Objective sleep parameter derived from overnight polysomnography: time in bed (TIB) in hours, measuring the total duration from lights-out to lights-on.
Time frame: Baseline and Post-Treatment (one-week after treatment conclusion)
Polysomnography - Total Sleep Time
Objective sleep parameter derived from overnight polysomnography: total sleep time (TST) in hours.
Time frame: Baseline and Post-Treatment (one-week after treatment conclusion)
Polysomnography - Sleep Efficiency
Objective sleep parameter derived from overnight polysomnography: sleep efficiency (SE) expressed as a percentage, calculated as total sleep time divided by time in bed.
Time frame: Baseline and Post-Treatment (one-week after treatment conclusion)
Polysomnography - Sleep Latency
Objective sleep parameter derived from overnight polysomnography: sleep latency in minutes, measuring the time interval from lights-off to the onset of the first scored sleep stage.
Time frame: Baseline and Post-Treatment (one-week after treatment conclusion)
Polysomnography - Wake After Sleep Onset
Objective sleep parameter derived from overnight polysomnography: wake after sleep onset (WASO) in minutes, measuring the total duration of wakefulness recorded after initial sleep onset.
Time frame: Baseline and Post-Treatment (one-week after treatment conclusion)