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