Investigation of the Effects of Sleep Fragmentation on Itch and Pain Sensitivity

Study Overview
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Brief Summary
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In This experiment, the investigators would like to test following hypotheses regarding the influence of sleep fragmentation on itch: To investigate similarity and differences between itch and pain by comparing the effect of sleep deprivation in them. To evaluate the inflammatory state induced by sleep fragmentation via the analysis of C-reactive protein (CRP) levels from blood samples. To correlate the anxiety and depression scores (evaluated through questionnaires) with itch and pain sensitivity and evaluate how they are affected by sleep fragmentation.

Detailed Description
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Chronic itch affects approximately a fifth of the global population and is associated with substantial negative consequences for the affected individuals. Furthermore, there is a lack of efficient treatment options for chronic itch. Poor sleep is a common companion of itch and is often reported by patients with chronic itch. Poor sleep is often characterized by nightly awakenings and troubles falling asleep. This is a significant problem as poor sleep in general is associated with lowered quality of life. While previous research has already established the negative impact of itch on sleep, it is yet to be studied whether the opposite tendency might be true as well. Knowledge about patients with chronic pain has shown that poor sleep can increase the sensitivity to pain and inflammation, and this tendency can also be observed in healthy participants after experimental sleep provocations. Therefore, the investigators wish to investigate how sleep provocations affect markers of itch in healthy participants.

Official Title
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Investigation of the Effects of Sleep Provocations on Itch and Pain Sensitivity

Conditions
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Cowhage, Histamine, Sleep Fragmentation

Intervention / Treatment
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* Other: Histamine
* Other: Cowhage


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Healthy men and women 18-60 years Speak and understand English Access to a smartphone during the experimental nights Exclusion Criteria: Pregnancy or lactation Drug addiction defined as any use of cannabis, opioids, or other drugs Previous or current history of neurological, dermatological, immunological musculoskeletal, cardiac disorder or mental illnesses (psychiatric diagnosis) that may affect the results (e.g., neuropathy, muscular pain in the upper extremities, anxiety, depression, schizophrenia etc.) Moles, wounds, scars, or tattoos in the area to be treated or tested Current use of medications that may affect the trial such as antihistamines and pain killers. Skin diseases Consumption of alcohol or painkillers 24 hours before the study days and between these Acute or chronic pain and itch Participation in other trials within 1 week of study entry (4 weeks in the case of pharmaceutical studies) Lack of ability to cooperate

Ages Eligible for Study
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Minimum Age: 18 Years
Maximum Age: 60 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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Accepts Healthy Volunteers

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Basic Science
Allocation: Non-Randomized
Intervention Model: Single Group Assignment
Interventional Model Description: The participants will be instructed to wake up at three designated timepoints for three consecutive nights at home.
Masking: None (Open Label)


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: Sleep fragmentation<br>This subproject will be conducted in two sessions separated by three nights of sleep fragmentation. Each session will last approximately 2 hours. At the beginning of the first visit and after the last visit, 9 ml of blood will be drawn, and plasma will be isolated. After plasma isolation, the CRP concentration will be analyzed. In each forearm of the participant, a 4x4 cm area will be selected as Area of Interest (AOI). In these selected areas, itch will be induced in both sessions using histamine and cowhage and several tests will be conducted. | Other: Histamine<br>* Histaminergic itch will be evoked by a 1% histamine solution. A droplet of histamine solution will be placed on the predetermined area on the forearm, and the SPT lancet will be pierced through the histamine with 120 g of pressure for 1-2 seconds<br>Other: Cowhage<br>* 25 spicules will be inserted in the centre of the predefined skin area on the mandibular area. The spicules will be gently rubbed for 15-20 seconds in circular motion to facilitate epidermal penetration<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Assessment of itch | Immediately following the itch provocations, participants will be instructed to rate the itch intensity for 10 minutes using a digital visual analogue scale (VAS; eVAS Software: Aalborg, University, Denmark), on a tablet. The scale will be measured from 0 to 100, where 0 represents 'no itch' and 100 'worst itch imaginable'. | Day 1: 1 minute after every itch inductions | 
| Assessment of itch | Immediately following the itch provocations, participants will be instructed to rate the itch intensity for 10 minutes using a digital visual analogue scale (VAS; eVAS Software: Aalborg, University, Denmark), on a tablet. The scale will be measured from 0 to 100, where 0 represents 'no itch' and 100 'worst itch imaginable'. | Day 2: 1 minute after every itch inductions | 
| Assessment of pain | Immediately following the itch provocations, participants will be instructed to rate the pain intensity for 10 minutes using a digital visual analogue scale (VAS; eVAS Software: Aalborg, University, Denmark), on a tablet. The scale will be measured from 0 to 100, where 0 represents 'no pain' and 100 'worst pain imaginable'. | Day 1: 1 minute after every itch inductions | 
| Assessment of pain | Immediately following the itch provocations, participants will be instructed to rate the pain intensity for 10 minutes using a digital visual analogue scale (VAS; eVAS Software: Aalborg, University, Denmark), on a tablet. The scale will be measured from 0 to 100, where 0 represents 'no pain' and 100 'worst pain imaginable'. | Day 2: 1 minute after every itch inductions | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Microvascular reactivity | The evoked cutaneous inflammation (quantified by superficial blood perfusion) will be measured by full-field laser perfusion imaging. | Day 1: 10 minutes after every itch inductions | 
| Microvascular reactivity | The evoked cutaneous inflammation (quantified by superficial blood perfusion) will be measured by full-field laser perfusion imaging. | Day 2: 10 minutes after every itch inductions | 
| Touch Pleasantness (TP) | Pleasant touch sensation measured using a standardized sensory brush (SENSELab Brush-05, Somedic AB, Hörby, Sweden) exerting a force of 200 to 400 mN. The stimulation consists of three strokes (2 cm in length) over the treated/control areas. The strokes will be applied perpendicularly to the skin and the subject will rate the sensation induced by the brush on a NRS scale labeled very unpleasant and very pleasant at the extremity and neutral at the center. | Day 1: 10 minutes after every itch inductions | 
| Touch Pleasantness (TP) | Pleasant touch sensation measured using a standardized sensory brush (SENSELab Brush-05, Somedic AB, Hörby, Sweden) exerting a force of 200 to 400 mN. The stimulation consists of three strokes (2 cm in length) over the treated/control areas. The strokes will be applied perpendicularly to the skin and the subject will rate the sensation induced by the brush on a NRS scale labeled very unpleasant and very pleasant at the extremity and neutral at the center. | Day 2: 10 minutes after every itch inductions | 
| Mechanically evoked itch (MEI), intensity approach | MEI is measured by using mildly pruritic, non-painful von Frey nylon filaments of a predetermined intensity (generally 5-30 miliNewton of force). This stimulator is moved in intervals of 0.5 cm outside the area of itch provocation. | Day 1: 10 minutes after every itch inductions | 
| Mechanically evoked itch (MEI), intensity approach | MEI is measured by using mildly pruritic, non-painful von Frey nylon filaments of a predetermined intensity (generally 5-30 miliNewton of force). This stimulator is moved in intervals of 0.5 cm outside the area of itch provocation. | Day 2: 10 minutes after every itch inductions | 
| Mechanically evoked itch, spatial approach | The von-Frey filament that better evokes the itch sensation during the assessment of mechanically evoked itch as well as a template of soft plastic are used to map the area of hyperkinesis in the test areas (forearms) | Day 1: 10 minutes after every itch inductions | 
| Mechanically evoked itch, spatial approach | The von-Frey filament that better evokes the itch sensation during the assessment of mechanically evoked itch as well as a template of soft plastic are used to map the area of hyperkinesis in the test areas (forearms) | Day 2: 10 minutes after every itch inductions | 
| Mechanical Pain Thresholds (MPT) | This test is conducted using a pinprick set (Aalborg University, Aalborg). The set consists of 7 needles each with a diameter of 0.6 mm and different force applications: 8, 16, 32, 64, 128, 256, and 512 mN. | Day 1: 10 minutes after every itch inductions | 
| Mechanical Pain Thresholds (MPT) | This test is conducted using a pinprick set (Aalborg University, Aalborg). The set consists of 7 needles each with a diameter of 0.6 mm and different force applications: 8, 16, 32, 64, 128, 256, and 512 mN. | Day 2: 10 minutes after every itch inductions | 
| Mechanical Pain Sensitivity (MPS), intensity approach | This test is conducted with the same pinprick set used to test the MPT. Starting with the lightest, each stimulator is applied at a rate of 2 s on, 2 s off in an ascending order, and the subject will be asked to give a pain rating for each stimulus on a scale from 0-10 (where 0 indicates ''no pain'', and 10 indicates the ''worst imaginable pain''). | Day 1: 10 minutes after every itch inductions | 
| Mechanical Pain Sensitivity (MPS), intensity approach | This test is conducted with the same pinprick set used to test the MPT. Starting with the lightest, each stimulator is applied at a rate of 2 s on, 2 s off in an ascending order, and the subject will be asked to give a pain rating for each stimulus on a scale from 0-10 (where 0 indicates ''no pain'', and 10 indicates the ''worst imaginable pain''). | Day 2: 10 minutes after every itch inductions | 
| Cold Detection Thresholds (CDT) and heat (HPT) detection | Thermal cold and heat stimuli will be applied by a contact heat-evoked potential stimulator (PATHWAYS; Medoc Ltd, Ramat Yishai, Israel), placed 5 cm distal to the elbow on the right dorsal forearm | Day 1: 10 minutes after every itch inductions | 
| Cold Detection Thresholds (CDT) and heat (HPT) detection | Thermal cold and heat stimuli will be applied by a contact heat-evoked potential stimulator (PATHWAYS; Medoc Ltd, Ramat Yishai, Israel), placed 5 cm distal to the elbow on the right dorsal forearm | Day 2: 10 minutes after every itch inductions | 
| Cold Detection Thresholds (CDT) and heat (HPT) pain thresholds | Thermal cold and heat stimuli will be applied by a contact heat-evoked potential stimulator (PATHWAYS; Medoc Ltd, Ramat Yishai, Israel), placed 5 cm distal to the elbow on the right dorsal forearm | Day 1: 10 minutes after every itch inductions | 
| Cold Detection Thresholds (CDT) and heat (HPT) pain thresholds | Thermal cold and heat stimuli will be applied by a contact heat-evoked potential stimulator (PATHWAYS; Medoc Ltd, Ramat Yishai, Israel), placed 5 cm distal to the elbow on the right dorsal forearm | Day 2: 10 minutes after every itch inductions | 
| Pain to Supra-threshold Heat Stimuli (STHS) | The tests will be conducted by using a PATHWAY ATS (Medoc Ltd, Israel) thermal sensory testing device. A thermode stimulator of 3x3 cm will be placed on the treated/placebo areas and kept in place by means of Velcro tape. The subjects will rate the pain to three suprathreshold heat pain stimuli (starting and ending at 32°C with an increase and decrease of 5°C and 3 s plateau at 50°C). | Day 1: 10 minutes after every itch inductions | 
| Pain to Supra-threshold Heat Stimuli (STHS) | The tests will be conducted by using a PATHWAY ATS (Medoc Ltd, Israel) thermal sensory testing device. A thermode stimulator of 3x3 cm will be placed on the treated/placebo areas and kept in place by means of Velcro tape. The subjects will rate the pain to three suprathreshold heat pain stimuli (starting and ending at 32°C with an increase and decrease of 5°C and 3 s plateau at 50°C). | Day 2: 10 minutes after every itch inductions | 
| Deep-tissue Pain Sensitivity Measurements | Deep-tissue pain sensitivity will be evaluated by cuff pressure stimuli using a computer-controlled cuff algometer (Cortex Technology and Aalborg University, Denmark) including a 13-cm wide tourniquet cuff (VBM, Sulz, Germany) and an electronic visual analog scale (VAS) (Aalborg University, Denmark) for recording of the pain intensity. | Day 1: 10 minutes after every itch inductions | 
| Deep-tissue Pain Sensitivity Measurements | Deep-tissue pain sensitivity will be evaluated by cuff pressure stimuli using a computer-controlled cuff algometer (Cortex Technology and Aalborg University, Denmark) including a 13-cm wide tourniquet cuff (VBM, Sulz, Germany) and an electronic visual analog scale (VAS) (Aalborg University, Denmark) for recording of the pain intensity. | Day 2: 10 minutes after every itch inductions | 
| Pressure Detection and Tolerance Threshold | The pressure will be increased by 1 kPa/s and the subject will be instructed to rate the pain intensity continuously on the electronic VAS until the tolerance level is reached. | Day 1: 10 minutes after every itch inductions | 
| Pressure Detection and Tolerance Threshold | The pressure will be increased by 1 kPa/s and the subject will be instructed to rate the pain intensity continuously on the electronic VAS until the tolerance level is reached. | Day 2: 10 minutes after every itch inductions | 
| Temporal Summation of Pain - TSP | A total of 10 repeated mechanical pressure stimuli at the PTT level will be delivered at 0.5 Hz (1 s stimulus duration and 1 s interval between stimuli) to the lower leg. A constant pressure of 5 kPa will be applied between the individual pressure stimuli to avoid movement of the cuff. During the 10 repeated stimuli, the subject will continuously rate the pain intensity on a 10 cm continuous VAS. | Day 1: 10 minutes after every itch inductions | 
| Temporal Summation of Pain - TSP | A total of 10 repeated mechanical pressure stimuli at the PTT level will be delivered at 0.5 Hz (1 s stimulus duration and 1 s interval between stimuli) to the lower leg. A constant pressure of 5 kPa will be applied between the individual pressure stimuli to avoid movement of the cuff. During the 10 repeated stimuli, the subject will continuously rate the pain intensity on a 10 cm continuous VAS. | Day 2: 10 minutes after every itch inductions | 
| Conditioned Pain Modulation - CPM | The concept of CPM is that a tonic painful stimulus (conditioning stimulus) will inhibit pain evoked simultaneously from another site (test stimulus). The painful conditioned stimulus will be applied simultaneously with the assessment stimulus. The conditioned stimulus will be terminated right after the subject presses the stop button. CPM will be defined as the difference between stimulus during and before the conditioned pain (i.e., during minus before). | Day 1: 10 minutes after every itch inductions | 
| Conditioned Pain Modulation - CPM | The concept of CPM is that a tonic painful stimulus (conditioning stimulus) will inhibit pain evoked simultaneously from another site (test stimulus). The painful conditioned stimulus will be applied simultaneously with the assessment stimulus. The conditioned stimulus will be terminated right after the subject presses the stop button. CPM will be defined as the difference between stimulus during and before the conditioned pain (i.e., during minus before). | Day 2: 10 minutes after every itch inductions | 
| The Itch Catastrophizing Scale | The itch catastrophizing scale is a modified version of the pain catastrophizing scale (PCS), which is a validated questionnaire measuring pain-related thoughts and feelings | Day 1 | 
| The Itch Catastrophizing Scale | The itch catastrophizing scale is a modified version of the pain catastrophizing scale (PCS), which is a validated questionnaire measuring pain-related thoughts and feelings | Day 2 | 
| The Pittsburg Sleep Quality Index (PSQI) | The PSQI consists of 19 items generating seven component scores: subjective sleep quality, sleep latency, sleep duration, habitual sleep efficiency, sleep disturbances, use of sleeping medication, and daytime dysfunction.. | Day 1 | 
| The Pittsburg Sleep Quality Index (PSQI) | The PSQI consists of 19 items generating seven component scores: subjective sleep quality, sleep latency, sleep duration, habitual sleep efficiency, sleep disturbances, use of sleeping medication, and daytime dysfunction.. | Day 2 | 
| The Hospital Anxiety and Depression Scale (HADS) | The HADS consists of 14 items with two 7-item subscales measuring anxiety and depression symptoms, respectively. | Day 1 | 
| The Hospital Anxiety and Depression Scale (HADS) | The HADS consists of 14 items with two 7-item subscales measuring anxiety and depression symptoms, respectively. | Day 2 | 
| Positive and Negative Affective Schedule | This 20-item instrument is a psychometric self-report test to assess affect (10 items for positive affect and 10 items for negative affect) and validated for the use in adolescents and adults | Day 1 | 
| Positive and Negative Affective Schedule | This 20-item instrument is a psychometric self-report test to assess affect (10 items for positive affect and 10 items for negative affect) and validated for the use in adolescents and adults | Day 2 | 
| Blood Sampling for C-Reactive Protein Analysis | Whole blood samples will be collected from the antecubital vein using a vacutainer blood collection device (S-Monovette, Sarstedt) with a 21-gauge needle. | Day 1 | 
| Blood Sampling for C-Reactive Protein Analysis | Whole blood samples will be collected from the antecubital vein using a vacutainer blood collection device (S-Monovette, Sarstedt) with a 21-gauge needle. | Day 2 |