Testing Solid State Lighting Countermeasures to Improve Circadian Adaptation, Sleep, and Performance During High Fidelity Analog and Flight Studies for the International Space Station (Lighting Effects) - 02.13.19

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Science Objectives for Everyone
The light bulbs on the International Space Station are being replaced with a new system designed for improved crew health and wellness. The Testing Solid State Lighting Countermeasures to Improve Circadian Adaptation, Sleep, and Performance During High Fidelity Analog and Flight Studies for the International Space Station (Lighting Effects) investigation studies the impact of the change from fluorescent light bulbs to solid-state light-emitting diodes (LEDs) with adjustable intensity and color and aims to determine if the new lights can improve crew circadian rhythms, sleep, and cognitive performance. Results from this investigation also have major implications for people on Earth who use electric lights.
Science Results for Everyone
Information Pending

The following content was provided by George C. Brainard, Ph.D., Steven W. Lockley, Ph.D., and is maintained in a database by the ISS Program Science Office.
Experiment Details

OpNom: Lighting Effects

Principal Investigator(s)
George C. Brainard, Ph.D., Thomas Jefferson University, Philadelphia, PA, United States
Steven W. Lockley, Ph.D., Brigham and Women's Hospital, Boston, MA, United States

Laura K. Barger, Ph.D., Harvard Medical School, Brigham and Women's Hospital, Boston, MA, United States
Charles A. Czeisler, Ph.D., M.D., Harvard Medical School, Brigham and Women's Hospital, Boston, MA, United States
Toni Clark, NASA Johnson Space Center, Houston, TX, United States
James Maida, NASA Johnson Space Center, Houston, TX, United States
Jason P. Sullivan, Brigham and Women's Hospital, Boston, MA, United States
Joseph M. Ronda, M.S., Brigham and Women's Hospital, Boston, MA, United States
Shadab A. Rahman, Ph.D., Brigham and Women's Hospital, Boston, MA, United States

NASA Johnson Space Center, Human Research Program, Houston, TX, United States

Sponsoring Space Agency
National Aeronautics and Space Administration (NASA)

Sponsoring Organization
NASA - Human Research Program (NASA-HRP)

Research Benefits
Earth Benefits, Space Exploration

ISS Expedition Duration
September 2016 - October 2019

Expeditions Assigned

Previous Missions
Information Pending

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Experiment Description

Research Overview

  • In August 2016, replacement of the General Luminaire Assemblies (GLAs) on the International Space Station (ISS) with Solid-State Light Assemblies (SSLAs) begins.
  • In addition to removing mercury from the ISS environment and providing more energy-efficient lighting, the SSLAs allow lighting properties (e.g., intensity, spectrum) to be changed to promote alertness and circadian resetting, or to promote sleep, as appropriate.
  • Testing Solid State Lighting Countermeasures to Improve Circadian Adaptation, Sleep, and Performance During High Fidelity Analog and Flight Studies for the International Space Station (Lighting Effects) looks at how the introduction of a Dynamic Lighting Schedule (DLS) benefits crew circadian rhythms, sleep, and cognitive performance, as compared to historical data collected under the old GLA lighting.
  • The DLS is based on basic and applied work examining the effect of light intensity and spectrum on human circadian rhythms, sleep, and alertness. First, there is a positive dose response between light intensity and the ability of light to reset the circadian clock and promote alertness and performance. Second, short wavelength (blue-appearing) light is most effective at resetting the circadian clock and promoting alertness and performance. Manipulation of light intensity and wavelength can be used to promote better sleep, alertness, and circadian adaptation.
  • In addition to providing standard lighting to promote good visual function, the DLS provides advice on when to use two other settings. The pre-bed setting of lower intensity, blue-wavelength-depleted light is intended for use for as long as possible before bed. A higher-intensity blue-light-enriched light setting is intended for use when elevated alertness or circadian adaptation is required.
  • The study is designed to generate quantitative data and knowledge for the benefit of crew health, habitability, environment, and human factors in the design of future human space flight vehicles and habitats. The study is also expected to provide guidance for flight surgeons, flight psychologists, and astronauts to help optimize sleep and circadian regulation during space exploration.


Spaceflight often exposes crew members to unusual sleep-wake and work schedules, including abnormal ‘day-lengths’ and abrupt ‘slam-shifts’ with late night work hours, which can lead to circadian pacemaker misalignment. Untreated circadian misalignment results in sleep and wake occurring at the incorrect circadian phase which, in turn, reduces sleep quality and quantity, impairs alertness, reaction time, and cognition, and increases risk of fatigue-related accidents. Even without circadian misalignment, sleep duration onboard the International Space Station (ISS) is usually poor (~6h/night) and hypnotic medications and caffeine are commonly used to address insomnia and daytime sleepiness. In such a high-risk environment as the ISS, the risk of fatigue-related performance decrements and accidents must be minimized.
Light is a powerful countermeasure for both circadian misalignment and sleepiness. The effects of light are safe, non-pharmacological and available from ambient lighting. Research has shown that monochromatic and narrow-bandwidth short-wavelength blue light are potent in suppressing nocturnal melatonin, phase-shifting the circadian pacemaker, and enhancing alertness and performance. Further, white-appearing light can be enriched in the blue portion of the spectrum to increase its potency to suppress melatonin, increase alertness, improve work performance and enhance sleep in healthy subjects. The enrichment of white-appearing light in the blue portion of the spectrum has strong potential as a safe, non-pharmacological countermeasure to reduce the risk of circadian misalignment and performance deficits during spaceflight.
Currently, the ISS uses General Luminaire Assemblies (GLAs) that house fluorescent lamps to illuminate the astronauts’ working and living environments. Importantly, the current supply of lamps for the GLAs will be depleted by 2017. Solid state light in the form of light-emitting diodes (LEDs) is an attractive candidate for replacing the GLAs onboard the ISS as well as all future manned space vehicles and habitats, and is advantageous over other sources due to lower upmass, power consumption, heat generation, and toxic materials, and longer lamp life expectancy.
A Dynamic Lighting Schedule has been developed based on the spectral and intensity sensitivity of the human circadian photoreceptor system. The Dynamic Lighting Schedule determines when each of three pre-determined light settings should be used to optimize lighting for different operational needs including to:
  1. facilitate circadian adaptation.
  2. enhance sleep.
  3. improve alertness and performance, while maintaining high visual acuity and color discernment for operational tasks.
Each setting has a unique intensity and spectrum to optimize its efficacy. Three pre-determined light settings are envisaged for use in different operational settings, and testing in both analog and flight studies is planned. The following specifications for Correlated Color Temperature (CCT) and luminance in candelas (cd) match Boeing’s vendor requirements for the settings:
  1. a General Illumination setting - 4500 K white light, 210 cd.
  2. a Phase Shift/Alertness setting - 6500 K (blue-enriched) white light, 420 cd.
  3. a Pre-Sleep setting - 2700 K (blue-depleted) white light, 90 cd or ideally lower. Further control, based on task or crew member preference, is possible via a dimmer switch or, in Crew Quarters, a shading system.
The aim of Testing Solid State Lighting Countermeasures to Improve Circadian Adaptation, Sleep, and Performance During High Fidelity Analog and Flight Studies for the International Space Station (Lighting Effects) is to test the efficacy of lighting protocols for daily operations using SSLAs for inflight crew members onboard ISS missions. The ultimate goal is to assess the acceptability, use, and operational impact of deployment of a Dynamic Lighting Schedule protocol on astronaut vision, sleep, alertness, circadian rhythms, and general well-being during flight missions aboard the ISS. This inflight study tests the hypothesis that compared to current static, daily lighting of General Illumination only, the Dynamic Lighting Schedule protocol:
  • maintains acceptable visual performance and color discrimination for operational tasks.
  • improves stability of circadian entrainment.
  • improves circadian adaptation following a sleep shift challenge (e.g., a ‘slam-shift’).
  • improves sleep duration and efficiency.
  • enhances wake-time alertness and cognitive performance.
After SSLA installation on ISS, comparison of the vision, sleep, performance, and circadian rhythm data collected before, during, and after an ISS mission to historical data collected by the research team, and others, during previous flight missions aboard ISS under GLA lighting is planned. These data are expected to provide a solid biological basis to verify the operational guidelines for in-flight use of the SSLAs and DLS.

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Space Applications
Spaceflight exposes crew members to sleep and wake schedules that do not follow the course of the sun. This can cause insomnia and fatigue, negatively affecting crew alertness and health. Lighting Effects studies new light sources that can be adjusted for intensity and wavelength across the day, simulating a more regular schedule. Results are expected to provide new information for flight surgeons, psychologists, and crew members to better regulate circadian rhythms and improve sleep. Engineers and designers may also benefit from this information as they build the next generation of crewed space exploration vehicles.

Earth Applications
Electric lighting is ubiquitous on Earth and can directly affect alertness. Anyone who uses electric lights can benefit from lights that can be adjusted for intensity and wavelength across the day, improving alertness during waking hours and promoting sleep during evening hours. Millions of people working night shifts would also benefit from a dynamic lighting schedule that mimics natural lighting.

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Operational Requirements and Protocols

A total of six in-flight subjects are required for this investigation. Additionally, historical control subjects are planned for recruitment by requesting data from past crew members who have participated in all of the Biochem Profile, Reaction Self Test, and Sleep studies.
Two in-flight sessions, each with two weeks of actigraphy and sleep logs, a 24-hour urine collection, and three performances of a cognitive test battery spread throughout a single day, are required, with one occurring after a period of standard crew sleep and one after a crew sleep shift.
Additionally, two visual performance tests (the Numerical Verification Test and Color Discrimination Test) are completed under each of four different, manually set SSLA settings plus one under GLA lighting at any point in the mission. Light meter readings at each of four different SSLA settings (plus under GLA lighting, in the cupola during ISS daylight, and in the dark) are also obtained every four weeks throughout a crew member’s stay on ISS.

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Decadal Survey Recommendations

Behavioral and Mental Health B2
Behavioral and Mental Health B3

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Results/More Information

Information Pending

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Related Websites

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Expedition 18 Commander, Mike Fincke, with an early version of a Solid State Lighting Assembly (the General Luminaire Assembly or GLA) in Node 2 of the ISS.

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NASA Image:  ISS049E028948 - Photographic documentation taken during Solid State Lighting Assembly (SSLA) Installation in the starboard Crew Quarters (CQ) by the Expedition 49 crew. The SSLAs were designed to replace General Luminaire Assemblies (GLAs) to improve visual acuity and to provide a crew health countermeasure for circadian rhythms, sleep, alertness and performance.

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