Light Intervention for Adaptation to Night Work

Study Results

Results pending

The study team has not published outcome measurements, participant flow, or safety data for this trial yet. Check back later for updates.

Basic Information

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Recruitment Status

COMPLETED

Clinical Phase

NA

Total Enrollment

97 participants

Study Classification

INTERVENTIONAL

Study Start Date

2017-08-25

Study Completion Date

2019-03-27

Brief Summary

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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.

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Detailed Description

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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).

Conditions

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Shift-Work Related Sleep Disturbance Sleep Deprivation Sleep

Study Design

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Allocation Method

RANDOMIZED

Intervention Model

CROSSOVER

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 Study Purpose

SUPPORTIVE_CARE

Blinding Strategy

SINGLE

Participants

Participants will not be given information on the hypotheses/ expected effects from the different interventions (light conditions).

Study Groups

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Light intensity, 1000 lux (4000 K)

Participants will work three consecutive simulated night shifts under full-spectrum LED-light, 1000 lux (4000 Kelvin) administered through standard room lighting.

Group Type EXPERIMENTAL

LED-light, 1000 lux

Intervention Type DEVICE

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.

Light intensity, 100 lux (4000 K)

Participants will work three consecutive simulated night shifts under full-spectrum LED-light, 100 lux (4000 Kelvin) administered through standard room lighting.

Group Type ACTIVE_COMPARATOR

LED-light, 100 lux

Intervention Type DEVICE

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.

Colour temperature, 7000 Kelvin

Participants will work three consecutive simulated night shifts under full-spectrum LED-light, 7000 K (200 lux) administered through standard room lighting.

Group Type EXPERIMENTAL

LED-light, 7000 K

Intervention Type DEVICE

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.

Colour temperature, 2500 Kelvin

Participants will work three consecutive simulated night shifts under full-spectrum LED-light, 2500 K (200 lux) administered through standard room lighting.

Group Type ACTIVE_COMPARATOR

LED-light, 2500 K

Intervention Type DEVICE

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 light, 455 nm

Participants work one night shift with blue LED-light (peak wavelength 455 nm) administered through standard room lighting.

Group Type EXPERIMENTAL

Blue LED-light

Intervention Type DEVICE

Blue light with peak wavelength 455 nm. Known to delay the circadian rhythm, suppress melatonin, and increase alertness.

Red light, 615 nm

Participants work one night shift with red LED-light (peak wavelength 615 nm) administered through standard room lighting.

Group Type ACTIVE_COMPARATOR

Red LED-light

Intervention Type DEVICE

Red light with peak wavelength 615 nm. Known not to affect the circadian rhythm, melatonin, and alertness.

Interventions

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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.

Intervention Type DEVICE

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.

Intervention Type DEVICE

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.

Intervention Type DEVICE

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.

Intervention Type DEVICE

Blue LED-light

Blue light with peak wavelength 455 nm. Known to delay the circadian rhythm, suppress melatonin, and increase alertness.

Intervention Type DEVICE

Red LED-light

Red light with peak wavelength 615 nm. Known not to affect the circadian rhythm, melatonin, and alertness.

Intervention Type DEVICE

Eligibility Criteria

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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

Minimum Eligible Age

19 Years

Maximum Eligible Age

30 Years

Eligible Sex

ALL

Accepts Healthy Volunteers

Yes