monitor data of 78 individual crew members from 80 shuttle flights (from 2001 to 2011) and 21
ISS missions (from 2005 to 2011) and found that, on average, space travelers get about 6 hours
of sleep per night while in space and only slightly more during the data collect interval
scheduled about three months prior to launch. The intensity of the pre-flight training and
travel schedule may have contributed to insufficient sleep in the pre-flight data collection
interval. During space missions, roughly three quarters of shuttle and ISS crew members
reported taking sleep-promoting medication. Shuttle crew members reported taking sleep-
promoting medications on about half of their nights in space, including nights prior to
performing extra vehicular activity (EVA) work the next day which were extra mentally and
physically demanding. The sleep-aid drug Zolpidem (brand name Ambien) was reported as the
most often taken by shuttle crew
members. The high prevalence of
sleeping pill use during spaceflight,
despite chronic sleep deficiency and
improved sleeping conditions and
quarters on the ISS, may suggest that
some other aspect of the space
environment, such as microgravity
itself, might contribute to sleep
disturbance. The use of sleep-
promoting medication did not
significantly increase the amount of
sleep that astronauts obtained
and only increased the sleep efficiency
of shuttle crew members by about one
percent. The minimal sleep
improvement on nights when sleep-promoting medications were used emphasizes the need for
further investigation into the stability, absorption, and effectiveness of such drugs in-
flight. Sleep and the use of sleep-promoting medications during spaceflight needs further
investigation, including the effect of chronic sleep deficiency and hangover effects from sleep
promoting medications on operational performance, to develop and recommend best practices
for ISS crew members. The sleep duration of crew members aboard long duration ISS missions
was similar to that of crew members aboard short-duration shuttle missions. Monitoring and
assessment of sleep duration and timing should continue in future spaceflight missions as a
medical requirement, including collection of baseline data before astronaut selection for flight
to estimate more accurately individual baseline sleep duration. Development of other more
effective countermeasures to promote sleep in-flight is crucial, and might include scheduling
modifications, strategically timed exposure to specific wavelengths of light and behavioral
strategies to ensure adequate sleep, which is essential for maintaining optimal health,
performance, and safety. Further research of sleep is planned for the future 1-year ISS
missions, twice the normal length of previous ISS missions, which might provide information on
trends in sleep over longer durations, which is especially relevant for future exploration class
missions beyond low Earth orbit.
ISS014E05119 – The Sleep-Long Actiwatch is visible on the
left arm of astronaut Michael Lopez-Alegria the Expedition 14
commander. The Actiwatch monitors light and activity
patterns of crew members.