Subjective and objective sleep variables, sleepiness and mood at D21 and D51.

Subjective and objective sleep variables, sleepiness, cortisol, mood and anxiety were assessed on the 21st day of the mission, D21, and 30 days later (after 10 shifts) at D51 = the 51st day. Values were compared using student “t” comparison tests between session-points. No significant differences were observed in subjective values of the quality of sleep and ease of falling asleep assessed on visual analogue scales (VAS) or sleep onset latencies (SOL) expressed in minutes (min) or on the number of awakenings. There was also no statistical difference in sleepiness over the last month on the Epworth sleepiness scale [11]. Objective sleep values measured by polysomnography (PSG) were also not significantly different between D21 and D51, including: SOL, total sleep period (TSP), total sleep time (TST), wake after sleep onset (WASO), sleep efficiency 1 (SE1) = TST/TSP, sleep efficiency 2 = TST/time in Bed (TIB), the percentages (%) of rapid eye movement (REM) sleep and slow wave sleep (SWS) and the REM latency. No significant difference was observed in the 12-hour night-cortisol excretion assessed on the same days. Mood and anxiety were assessed based on the profile of mood state (POMS) six dimensions [12] and no significant differences were observed except for confusion, which was significantly higher on D51. Normal range values: Subjective values: Sleepiness was assessed using the Epworth sleepiness scale (ESS), referring to the month prior to the assessment: a score of 10 or more indicated that the subject was sleepy; a score of 16 or more indicated being very sleepy (12). Objective values: in a young and healthy group of subjects normal SOL is under 30 minutes, common total sleep time in adults is around 420 minutes, normal REM latency is above 60 minutes, normal % of REM sleep is above 20% and % of SWS is above 20%. Normal WASO in less than 60 minutes, normal SE is above 90% (Ohayon et al., 2004).
Subjective and objective sleep variables, sleepiness and mood at D21 and D51.