Sleep quality may be disturbed in crowded, isolated environments such as the International Space Station (ISS) and the Aquarius habitat. Potential disturbances in the sleep/wake cycles of astronauts and aquanauts compared to ground-based sleep/wake cycles need to be defined in order to understand its consequences on human performance and well-being. The purpose of this study is to quantitate objective measures of sleep quality such as sleep duration, sleep latency and sleep efficiency with a non-intrusive wrist-worn sleep/wake activity monitor known as the Actiwatch®. Crewmembers wore the Actiwatch® on the non-dominant hand at all times while inside the habitat. A record of activities and sleep was kept, including in-suit Doppler use. The collection of actigraphy data with an Actiwatch® allowed an objective measure of crewmember activity and sleep quality. Altered activity and sleep quality data were correlated with data obtained in the in-suit Doppler and STARx/ARES studies.
Baseline sleep/wake measurements were recorded for five days approximately three weeks prior to the mission. During the NEEMO 5 mission, Actiwatches® were worn on the non-dominant hand at all times while inside the habitat. The watches were removed for dives. The Actiwatch® Activity Log reflects don/doff of the Actiwatch® along with sleep/wake and dive times, as well as in-suit Doppler use.
The average illumination during the mission decreased significantly (p<0.05). All four aquanauts completed six days/five nights of actigraphy data collection approximately two-weeks prior to the mission. Three of four aquanauts were able to complete 14 days/13 nights of actigraphy data collection during the two-week mission in the Aquarius habitat. An increase of 9 minutes was observed in sleep latency during the mission, however this difference is not statistically significant.
One aquanaut failed to collect data on days three and 11 to 14 because the original and spare Actiwatches® were submersed in saltwater (Actiwatches® are advertised to not be water proof). This same aquanaut also failed to wear the Actiwatch® during the sleep period of day nine.
The crew reported that Actiwatches® are water-resistant as the two splashed watches continued collecting data after being momentarily submerged during the mission. Remembering to record the doff and don times was the only inconvenience. Crewmembers recommended that all bands should be Velcro for easy doff and don and having a time display incorporated into the watch to make logging times easier.