Light Intervention for Adaptation to Night Work

Sleep Clinical Trial

Official title:

Effects of Bright Light Intervention for Adaptation to Night Work: Shift Work Simulation Experiments

Clinical Trial Details — Status: Completed

Administrative data

• NCT number: NCT03203538
• Other study ID #: 270755
• Status: Completed
• Phase: N/A
• Start date: August 25, 2017
• Est. completion date: March 27, 2019

Study information

• Verified date: February 2018
• Source: University of Bergen
• Contact: n/a
• Is FDA regulated: No
• Study type: Interventional

Clinical Trial Summary

The project will contribute with new knowledge concerning how aspects of the physical work environment (lighting conditions) can be arranged to facilitate the workers' adaptation to night work. This is important given the reported adverse consequences of shift work for performance, safety, and health. The project involves a series of three experimental, laboratory based shift work simulation studies. The aim is to investigate how different lighting conditions (intensities and colour temperature), administered through light emitting diode (LED) based bright light integrated standard room lighting, affects adaptation to three consecutive simulated night shifts and re adaptation to a day oriented schedule on measures of alertness, cognitive performance, sleep and circadian rhythm. The proposed project examines the effects of interventions that can be applied in naturalistic settings and will be based on new laboratory infrastructure available at the laboratories situated in the Faculty of Psychology, University of Bergen.

Description:

Bright light has been suggested as a countermeasure to the negative impact of night work in terms of safety, performance and subsequent sleep. The effect depends on the timing of light (e.g, phase-response curve), duration of light exposure and the intensity of light, as well as the wavelengths that are emitted. Exposure to bright light (more intense than typical room lightning), at evening and night, has been effective in delaying the circadian rhythm to sufficiently adapt to night work both in simulated night work, and in field studies of workers. Blue light has significantly stronger phase shifting effects than other wavelengths of the visible spectrum. The effect of light on the circadian system is mediated by retinal photoresponsive cell population (intrinsically photoresponsive retinal ganglion cells; ipRGC) that contains the photopigment melanopsin, highly sensitive to blue light. These cells signal directly to the suprachiasmatic nuclei (SCN) of the hypothalamus, the circadian pacemaker. Bright light has also been reported to improve alertness and performance during night shifts.

To the best of the investigators knowledge, no shift work simulation study has made the full advance of LED-technology in terms of using light administered via standard room lighting on adaptation to night work. Today, new LED-technology represents an excellent opportunity to study this as roof mounted LED-sources integrated as standard indoor lightening can be programmed to provide a wide range of light intensities and colour temperatures. LED-sources have the advantage over standard light therapy that subjects can be exposed to the therapy via standard room lightening (not confined to a special therapy lamp) thereby allowing the workers to conduct work tasks as normal during light exposure.

Against this backdrop this project aims to investigate how different lighting conditions, administered through LED-based bright light integrated standard room lighting, affects adaptation to three consecutive simulated night shifts and re adaptation to a day oriented schedule on measures of alertness, cognitive performance, sleep and circadian rhythm. In addition, measures of mood, appetite, heart rate variability (HRV), pain sensitivity, moral reasoning, and inflammatory markers will be examined. The researchers also aim to investigate the effects of two extreme monochromatic light conditions (blue vs. red) based on integrated standard room lighting on the adaptation to one simulated night shift.

Study participants will work simulated night shifts (11:00 pm to 07:00 am) in a light laboratory where light parameters (intensity and colour temperature) can be manipulated via roof mounted LED-sources integrated as standard indoor lightening. Participants will be recruited among students at the University of Bergen, and a screening will be done to ensure healthy participants fit for the study. The included participants will take part in experiments with two bouts of three consecutive simulated night shifts (6 nights in total).

HRV will be measured throughout the night shift, and five times, approx. every 1.5 hour (11:30 pm, 01:00 am, 02:30 am, 04:00 am, 05:30 am), the subjects will be tested on a test battery of cognitive tests and will rate their subjective sleepiness. Sleep will be assessed by sleep diary and actigraphy 3 days prior to, during, and 3 days following the shifts. One day before the night shift and the day after the night shift period the circadian rhythm will be measured by saliva samples for estimation of dim light melatonin onset. Prior to-, during- and after the night shifts, participants will undergo a pain sensitivity test. Blood spot samples will be collected at the beginning and the end of each night shift for analysis of inflammatory markers (e.g. interleukins).

Recruitment information / eligibility

• Status: Completed
• Enrollment: 97
• Est. completion date: March 27, 2019
• Est. primary completion date: March 27, 2019
• Accepts healthy volunteers: Accepts Healthy Volunteers
• Gender: All
• Age group: 19 Years to 30 Years

Eligibility

Inclusion Criteria:

• Participants are physical and mentally healthy (assessed with BMI and 'General Health Questionnaire-12')

• Participants accept to comply with the protocol (refrain from alcohol, tobacco and coffee, and retain regular bed- and wake-times the week before the simulated night shifts)

Exclusion Criteria:

• Neurological, psychiatric or sleep related disorders ('Bergen Insomnia Scale', 'global sleep assessement questionnaire')

• Extreme 'morningness-eveningness' type ('Horne Östberg morningness eveningness questionnaire')

• Use of medication

• Worked night shifts the last 3 months

• Travelled through more than two time zones the last 3 months

Related Conditions & MeSH terms

• Dyssomnias
• Parasomnias
• Shift-Work Related Sleep Disturbance
• Sleep
• Sleep Deprivation
• Sleep Wake Disorders

Intervention

Device:
• LED-light, 1000 lux
Full-spectrum light, 1000 lux, 4000 K. Represent a light intensity within acceptable range (light that is not too glary); 4000 K is among the most commonly used indoor light colour temperatures.
• LED-light, 100 lux
Full-spectrum light, 100 lux, 4000 K. Represent a light intensity within acceptable range (light that provides sufficient eye sight); 4000 K is among the most commonly used indoor light colour temperatures.
• LED-light, 7000 K
Full-spectrum light, 7000 K, 200 lux. Represent the upper border of common colour indoor light temperature, 200 lux is a common indoor light intensity.
• LED-light, 2500 K
Full-spectrum light, 2500 K, 200 lux. Represent the lower border of common colour indoor light temperature, 200 lux is a common indoor light intensity.
• Blue LED-light
Blue light with peak wavelength 455 nm. Known to delay the circadian rhythm, suppress melatonin, and increase alertness.
• Red LED-light
Red light with peak wavelength 615 nm. Known not to affect the circadian rhythm, melatonin, and alertness.

Locations

Country	Name	City	State
Norway	The faculty of psychology, University of Bergen	Bergen	Hordaland

Sponsors (2)

Lead Sponsor	Collaborator
University of Bergen	Glamox

Country where clinical trial is conducted

Norway, 

Outcome

Type	Measure	Description	Time frame	Safety issue
Primary	Cognitive performance	Cognitive performance will be measured using the Psychomotor Vigilance Test (PVT). The PVT measures sustained attention, and is considered the 'gold standard' for assessing the effects of sleep deprivation on cognition. The task will be performed approx. every 1.5h throughout the nightshifts.	3 nights
Primary	Circadian phase	Circadian phase will be measured through assessement of 'Dim Light Melatonin Onset' (DLMO). Saliva samples will be collected every hour in the evening (from 7 pm) to one hour past regular bedtime, one day before the first night shift and the day after the night shift period. Saliva will be analyzed for melatonin, giving an estimate on DLMO.	5 days-nights
Primary	Sleep	Sleep will be measured objectively using actigraphy	9 days-nights
Secondary	Subjective sleepiness	Karolinska Sleepiness Scale (KSS) will be used to assess subjective sleepiness throughout the night shifts. KSS is a likert scale ranging from 1-9, where subjects rate their sleepiness. '1' indicates 'extremely alert', '9' indicates 'very sleepy/fighting sleep'.	3 nights
Secondary	Self-reported sleep	A sleep diary will be used.	9 days-nights
Secondary	Heart rate variability	'Heart Rate Variability' will be assessed by using Polar heart rate monitor V800 that will continuously monitor 'HRV' through the night.	3 nights
Secondary	Interleukin	Blood spot samples will be analyzed for interleukins (IL-2, IL-4, IL-5, IL-6, IL-8, IL-10, IL-13)	3 nights
Secondary	Granulocyte macrophage colony-stimulating factor (GM-CSF)	Blood-spot samples will be analyzed for GM-CSF.	3 nights
Secondary	Interferon gamma (IFN-gamma)	Blood-spot samples will be analyzed for IFN-gamma.	3 nights
Secondary	Tumor necrosis factor alpha (TNF-a)	Blood-spot samples will be analyzed for TNF-a	3 nights
Secondary	Positive and negative affect	'Positive and Negative Affect Schedule', will be administered to assess mood.	3 nights
Secondary	Pain sensitivity	By using a handheld pressure algometer, Wagner FPIX Force One, the pressure pain threshold will be measured. The test site will be the trapezius muscle, and the pressure will be increased in steps of 5 N/sec until the participant indicates pain.	3 nights
Secondary	Headache and eyestrain	A 'Headache and Eyestrain Scale' will be used to get subjective measures on how participants perceive the lighting conditions.	3 nights
Secondary	Appetite/ food cravings	Appetite/ food cravings for different food types will be assessed using a visual analogue scale to record response to questions like: "How much would you like to eat xxx right now?"; A 'Dot-probe test' provides measure of attentional bias towards various food types (pictures)	3 nights
Secondary	Working memory	A 'Working Memory Scanning Task' measure ability to encode and maintain information in working memory	3 nights
Secondary	Decision/ response execution	A 'Two-Choice Numerosity Discrimination Task' measure decision criterion and response execution	3 nights
Secondary	Decision/ response inhibition	A 'Reversal Learning Decision Task' measure ability to adjust choices/ response inhibition	3 nights
Secondary	Cognitive control	A 'Task Switching-Performance Test' measure cognitive control	3 nights
Secondary	Planning	The 'Tower of Hanoi Test' measure planning and sequencing abilities	3 nights
Secondary	Moral reasoning	the 'Defining Issues Test' measure moral reasoning.	3 nights
Secondary	Cognitive throughput	A 'Digit Symbol Substitution Test' will be used as a measure of cognitive throughput	3 nights
Secondary	Fine motor skills	The 'grooved pegboard test' assess fine motor skills through the night shifts	3 nights
Secondary	Recognition of emotions	An 'emotional hexagon test', were participants rate standardized pictures of faces expressing different emotions, measure the ability to discriminate between emotional expressions.	3 nights
Secondary	Pupil size	Pupil size will be measured, using a tobii eyetracker, three times during night shifts. This can provide an objective measure of sleepiness.	3 nights
Secondary	Core body temperature	To get a secondary measure of circadian phase, core body temperature will be measured using ingestible temperature capsules.	1-2 nights
Secondary	Leadership evaluation	The 'Multifactor Leadership Questionnaire' will be used to assess participants leadership preferences. The questionnaire will be administered during daytime and during night shifts.	2 nights, 1 day
Secondary	Experiences of perceptual anomalies	The Cardiff Anomalous Perceptions Scale (CAPS) questionnaire will be administered after the night shifts to assess experiences of hallucinations and perceptual anomalies during night shifts. The questionnaire consists of 32 items/questions regarding perceptual anomalies, e.g. "Do you ever notice that sounds are much louder than they normally would be?", that are answered with 'yes' or 'no'. Adding up the number of 'yes' answers gives the CAPS Total Score ranging from 0 (low) to 32 (high). For each item endorsed, participants rate the item for distress, intrusiveness and frequency, giving three subscales. The rating for subscales goes from 1 (low) to 5 (high). Nonendorsed items are considered to have a score of 0 on subscales. For each subscale the possible range goes from 0 (low) to 160 (high).	3 nights
Secondary	Objective sleepiness, sleep and sleep stages	A subgroup of participants (12-16 in each experiment) will be subject to electroencephalography (EEG) during night shifts, and polysomnography (PSG) after night shifts. EEG will provide a measure of electrical activity in the brain during wakefulness, and can provide an objective measure of sleepiness. PSG will be conducted in the sleep period after night shifts, and allow for the scoring of sleep stages. PSG is considered the gold standard for measuring sleep.	3 nights and sleep periods