By Kate Greene
Sleeping in space is tricky. Loud machines on the space shuttle and space station and floating-arm awkwardness in low gravity can keep astronauts awake. Plus, there’s no 24-hour sunrise and sunset cycle to cue the body’s circadian system.
Missing a few hours of sleep isn’t so bad for astronauts on short jaunts to low-earth orbit. But astronauts deprived of sleep over the longterm are less alert and perform poorly on certain cognitive tests. This means sleep deprivation on a multi-year mission to Mars mission could become a serious problem.
Currently, the most popular fix for restless nights is sleeping pills. But could it be possible to regulate astronauts’ circadian systems without drugs? Perhaps even more effectively? I’m interested in finding a non-pharmaceutical and easy-to-implement way to improve astronauts’ sleep. A successful treatment could also help Earthbound night-shift workers and those who suffer from insomnia.
Some researchers believe that exposure to bright, blue-white light in the mornings can help keep the circadian system healthy. Special receptor cells in our eyes detect blue light. These cells have a direct connection to the seat of our circadian system in our brain, a region called the suprachiasmatic nucleus. Additionally, bright blue-white light has been shown to suppress melatonin, a hormone associated with sleep, and to increase alertness. And for years psychologists have known that bright morning light is an effective treatment for depression, specifically Seasonal Affective Disorder.
It’s an appealing solution to sleep problems: simply set the lights on the space station, spacecraft, or Mars habitat to morning exposure and let the brain naturally reset. But right now, there’s not much data about how such light exposure affects sleep quality in normal, healthy adults.
My goal is to collect many months worth of sleep data from myself and my HI-SEAS crew mates. We’ll use the Zeo Bedside Sleep Manager to track the duration of sleep cycles and the time it takes us to fall asleep each night. During experimental phases, we’ll be exposed to bright blue-white light first thing in the morning. Ultimately, I’m interested in testing the hypothesis that such a lighting intervention will reduce the time it takes to fall asleep and increase the time spent in deep and REM sleep.
If all goes well, the sleep study might help fill gaps in NASA’s Human Research Roadmap. It could also create a foundation for systematic studies of sleep and lighting in a Mars habitat environment. And finally, it might lead to potential, viable alternative to drugs for treating sleep disorders here on Earth.
Putcha, L., et al. “Pharmaceutical use by US astronauts on space shuttle missions.” Aviation, space, and environmental medicine 70.7 (1999): 705-708.
Whitmire, Alexandra M., et al. “Risk of performance errors due to sleep loss, circadian desynchronization, fatigue, and work overload.” Evidence-Based Review by NASA Behavioral Health and Performance Program, Johnson Space Center (2009): 85-117.
Thapan, Kavita, Josephine Arendt, and Debra J. Skene. “An action spectrum for melatonin suppression: evidence for a novel non-rod, non-cone photoreceptor system in humans.” The Journal of physiology 535.1 (2001): 261-267.
Lockley, Steven W., et al. “Short-wavelength sensitivity for the direct effects of light on alertness, vigilance, and the waking electroencephalogram in humans.” Sleep-New York Then Westchester- 29.2 (2006): 161.
Terman, Jiuan Su, et al. “Circadian time of morning light administration and therapeutic response in winter depression.” Archives of General Psychiatry58.1 (2001): 69.
Dowling, Glenna A., et al. “Effect of morning bright light treatment for rest-activity disruption in institutionalized patients with severe Alzheimer’s disease.” International psychogeriatrics 17.2 (2005): 221-236.
Ancoli-Israel, Sonia, et al. “Increased light exposure consolidates sleep and strengthens circadian rhythms in severe Alzheimer’s disease patients.”Behavioral Sleep Medicine 1.1 (2003): 22-36.
Shambroom, John R., Stephan E. Fábregas, Jack Johnstone. “Validation of an automated wireless system to monitor sleep in healthy adults.” Journal of Sleep Research 21.2 (2011): 221-230.
NASA’s Human Research Roadmap Sleep and Lighting Gap http://humanresearchroadmap.nasa.gov/Gaps/?i=406
By Kate Greene