STS-95 PAYLOADS - Human Research
Sleeping Better in Space: Sleep Studies and Clinical Trials of Melatonin as a Hypnotic

Astronauts can have difficulty sleeping during space flight. Most likely, a combination of factors contributes to these sleep problems. These factors include the novelty and excitement of space flight itself, ambient noise in the close confines of the spacecraft, and the absence of normal day/night cycles. In fact, the sun rises and sets every 90 minutes in low Earth orbit.

Sleep disruption can lead to fatigue and decrements in performance for astronauts. To improve sleep quality, many astronauts take sleep aids such as the benzodiazepine hypnotic Restoril. These medications, however, may have undesirable side effects on performance and mental alertness. In the search for a better sleep aid, researchers have targeted melatonin, a naturally occurring hormone produced in the pineal gland of the brain. Ground-based research indicates that melatonin may facilitate sleep, an attribute that is particularly important if astronauts are scheduled to sleep at a time of day when their bodies are not producing the hormone.

The investigation, Clinical Trial of Melatonin as a Hypnotic, will determine whether the use of melatonin improves the quality of sleep for astronauts during space flight, thereby improving their ability to perform the mentally challenging and physically rigorous tasks required of them. Although melatonin is currently available in health food stores as a food supplement, the dosages available are typically 10-20 times greater than levels found in the human body. This study is designed to evaluate whether a near-physiologic dose of the hormone can be effective in promoting sleep.

Payload Specialist John Glenn prepares to climb into his sleep station. He is wearing a suit and headset equipped with monitoring instruments to gather data as he sleeps.

Aside from improving the sleep quality of astronauts during space flight, this research has direct application for many people here on Earth. Sleep disorders affect a wide range of people from those who perform challenging jobs involving night shift work to the many Americans who often experience sleep disorders as they age. This investigation will be the first to assess the effects of space flight on the sleep patterns of an older astronaut.

The sleep quality and mental functions of crewmembers will be assessed before, during, and after flight. Before each sleep period of the mission, crewmembers will take an unmarked capsule that contains either melatonin or placebo. The crewmembers will wear an unobtrusive wrist actigraph to monitor their sleep-wake cycle. In addition, astronauts' sleep will be characterized more completely via recordings that assess several sleep parameters. During each of the four intensive monitoring sessions, crewmembers will wear an electrode net on their heads . These electrodes will be connected to a Digital Sleep Recorder that monitors brain waves, eye movements, muscle tension, body movements, and respiration. Astronauts will be assisted in troubleshooting this high-tech setup by an artificial intelligence computer system developed jointly by the Massachusetts Institute of Technology and NASA Ames.

Other factors related to sleep quality, such as mental performance and environmental parameters, will also be assessed to complement data collected with the sleep recorder. After each night of wearing the electrode net, crewmembers will use a laptop computer to fill out a record of sleep quality and complete a 20-minute battery of cognitive performance and subjective mood tasks. Body temperature will be recorded continuously from flight day 2 through flight day 9 using an ingested radio-telemetry pill. These readings will be compared with similar recordings pre- and postflight.

Ambient light levels in work and rest areas will also be measured to correlate environmental light cues with sleep patterns. Crew members will don the electrode net for six nights of monitoring before flight and three nights of monitoring after flight to complement the data collected inflight.