Clinical trial NCT03203538: Light Intervention for Adaptation to Night Work
Official title: Effects of Bright Light Intervention for Adaptation to Night Work: Shift Work Simulation Experiments
Study type: INTERVENTIONAL
Overall status: COMPLETED
Phase: NA
Conditions: Shift-Work Related Sleep Disturbance
Sleep Deprivation
Sleep
Keywords: night work
shift work
light
bright light
sleep
cognitive performance
circadian rhythm
Lead sponsor: University of Bergen
Sponsor class: OTHER
Collaborators: name: Glamox
First posted: 2017-06-29
Enrollment: 97
Sex: ALL
Minimum age (years): 19
Maximum age (years): 30
Standard ages: ADULT
Accepts healthy volunteers: yes
Allocation: RANDOMIZED
Intervention model: CROSSOVER
Intervention model description: Three related night shift studies have been planned. Each study investigates how different lighting conditions, administered through LED-based bright light integrated standard room lighting, affects adaptation to simulated night shifts and re adaptation to a day oriented schedule.

In each study, 28 participants (84 in total) will be exposed to the interventions (light conditions) in a randomized, blinded, controlled, crossover study.

The simulated night shifts will last from 11pm to 7am. The specific light conditions will last from 11pm to 5am (study 1: 1000 lux vs. 100 lux; study 2: 7000 K vs. 2500 K; study 3: 455 nm vs. 615 nm) where after (from 5am to 7am) all participants will be exposed to the same light conditions (200 lux, 4000 K). After completion of one bout of night work (three consecutive shifts for study 1 and 2; one night shift for study 3) there will be a washout period of four weeks before the participants cross over.
Primary purpose: SUPPORTIVE_CARE

Brief 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.

Detailed 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).

Eligibility criteria: 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

Primary outcomes:
measure: Cognitive performance
timeFrame: 3 nights
measure: Circadian phase
timeFrame: 5 days-nights
measure: Sleep
timeFrame: 9 days-nights
Secondary outcomes:
measure: Subjective sleepiness
timeFrame: 3 nights
measure: Self-reported sleep
timeFrame: 9 days-nights
measure: Heart rate variability
timeFrame: 3 nights
measure: Interleukin
timeFrame: 3 nights
measure: Granulocyte macrophage colony-stimulating factor (GM-CSF)
timeFrame: 3 nights
measure: Interferon gamma (IFN-gamma)
timeFrame: 3 nights
measure: Tumor necrosis factor alpha (TNF-a)
timeFrame: 3 nights
measure: Positive and negative affect
timeFrame: 3 nights
measure: Pain sensitivity
timeFrame: 3 nights
measure: Headache and eyestrain
timeFrame: 3 nights
measure: Appetite/ food cravings
timeFrame: 3 nights
measure: Working memory
timeFrame: 3 nights
measure: Decision/ response execution
timeFrame: 3 nights
measure: Decision/ response inhibition
timeFrame: 3 nights
measure: Cognitive control
timeFrame: 3 nights
measure: Planning
timeFrame: 3 nights
measure: Moral reasoning
timeFrame: 3 nights
measure: Cognitive throughput
timeFrame: 3 nights
measure: Fine motor skills
timeFrame: 3 nights
measure: Recognition of emotions
timeFrame: 3 nights
measure: Pupil size
timeFrame: 3 nights
measure: Core body temperature
timeFrame: 1-2 nights
measure: Leadership evaluation
timeFrame: 2 nights, 1 day
measure: Experiences of perceptual anomalies
timeFrame: 3 nights
measure: Objective sleepiness, sleep and sleep stages
timeFrame: 3 nights and sleep periods
Other outcomes:
Locations:
city: Bergen
country: Norway
facility: The faculty of psychology, University of Bergen
state: Hordaland
Study officials:
affiliation: University of Bergen, department of psychosocial science
name: Erlend Sunde
role: PRINCIPAL_INVESTIGATOR
References:
citation: Sunde E, Mrdalj J, Pedersen TT, Bjorvatn B, Gronli J, Harris A, Waage S, Pallesen S. Bright light exposure during simulated night work improves cognitive flexibility. Chronobiol Int. 2022 Jul;39(7):948-963. doi: 10.1080/07420528.2022.2050922. Epub 2022 Mar 28.
citation: Sunde E, Pedersen T, Mrdalj J, Thun E, Gronli J, Harris A, Bjorvatn B, Waage S, Skene DJ, Pallesen S. Alerting and Circadian Effects of Short-Wavelength vs. Long-Wavelength Narrow-Bandwidth Light during a Simulated Night Shift. Clocks Sleep. 2020 Nov 25;2(4):502-522. doi: 10.3390/clockssleep2040037.
citation: Sunde E, Pedersen T, Mrdalj J, Thun E, Gronli J, Harris A, Bjorvatn B, Waage S, Skene DJ, Pallesen S. Blue-Enriched White Light Improves Performance but Not Subjective Alertness and Circadian Adaptation During Three Consecutive Simulated Night Shifts. Front Psychol. 2020 Aug 18;11:2172. doi: 10.3389/fpsyg.2020.02172. eCollection 2020.
citation: Sunde E, Mrdalj J, Pedersen T, Thun E, Bjorvatn B, Gronli J, Harris A, Waage S, Pallesen S. Role of nocturnal light intensity on adaptation to three consecutive night shifts: a counterbalanced crossover study. Occup Environ Med. 2020 Apr;77(4):249-255. doi: 10.1136/oemed-2019-106049. Epub 2020 Feb 4.