Assessing Individual Differences in Adaptation to Extreme Environments: A 36-Hour Sleep Deprivation Study

In space, astronauts may experience effects of cumulative sleep loss due to demanding work schedules that can result in cognitive performance impairments, mood state deteriorations, and sleep-wake cycle disruption. The study objectives were: 1) to examine the effects of 36-hours of sleep deprivation on cognitive performance, mood states, and physiological responses; and 2) to identify which metrics best predict fatigue induced performance decrements. Five subjects (3 men, and 2 women) participated in a 36-hour sleep deprivation study over a four day period: Days 1 and 2 (training on cognitive task battery during a typical sleep-wake period); Day 3 (onset of sleep deprivation), Day 4 (end of sleep deprivation, resume normal sleep cycle), and after waking, post-test measures on performance battery. Cognitive performance was measured using the Delta performance test battery that included seven subtests measuring neuro-motor, perceptual, and cognitive skills. Mood alterations were evaluated using a 10-point analog scale consisting of seven specific mood states. The tests were administered at three-hour intervals during the 36-hour sleep deprivation period.  An ambulatory physiological monitor was used to continuously record heart rate, respiration rate, skin temperature, posture, and activity.  Results indicate that sleep deprivation negatively impacts cognitive performance and subjective mood states. Individual results varied in the time of onset, the severity of performance declines, and the rate of recovery following sleep deprivation.  Physiological responses during sleep deprivation differed from those measures obtained during a typical sleep-wake period (Day 1), and varied between individuals.