Elsevier

Neuroscience Letters

Volume 516, Issue 2, 16 May 2012, Pages 177-181
Neuroscience Letters

Working hours, sleep, salivary cortisol, fatigue and neuro-behavior during Mars analog mission: Five crews study

https://doi.org/10.1016/j.neulet.2012.03.067Get rights and content

Abstract

The buoyancy of humans in exploring extreme space environments has been established during missions to the moon. Long duration missions like mission to Mars however, requires humans to adapt to systemic and complex environments beyond the human body's capacity. Astronauts will encounter both physiological and psychological extremes during this trip. Very few studies are conducted on effect of long duration work and sleepiness on cognitive performance. So, this study was planned to find out effects of leadership responsibility, sleepiness and long duration working hours on cognitive performance. The 30 members (leadership: normal; 10:20) were selected from MDRS crews (Mars Desert Research Station, USA). Neurobehavioral test performance, self-ratings of fatigue and sleepiness, and salivary cortisol levels were evaluated during first day, mid and end day of mission. The leadership group did not show any signs of reduced test performance, even in elevated fatigue and sleepiness. The leadership group had faster reaction times on end of mission as compared to first and after 7 day of mission. Salivary cortisol levels were significantly higher in leadership group as compared to normal group. The results suggest that long duration work and sleepiness does not affect the cognitive performance of crew member. Further study is required while taking into account all factors and large sample size to prove this fact.

Highlights

► To investigate the effect of sleepiness and long duration working hours on cognitive performance. ► Neurobehavioral test performance, fatigue, sleepiness, and salivary cortisol levels were evaluated. ► Increased levels of salivary cortisol levels, working hours and sleepiness were not significantly affect the cognitive performance.

Introduction

From the beginning of the space age, physicians, human factors engineers, medical experts and psychologists expressed their concerns about astronaut's abilities to meet the physical, physiological, psychological requirements including neurobehavioral and interpersonal demands of working in space [13], [17], [4]. Neurobehavioral and physical deterioration is experienced due to insufficient sleep and long working hours in astronauts during long-duration manned space flights [10]. The performance and working ability of astronauts during long duration space flight depends heavily on achieving recovery through adequate sleep. Sleep loss and long working hours can affect the fundamental elements of human performance capability including vigilance, cognitive speed and accuracy, working memory, reaction time, and physiological alertness [10], [2]. In some conditions, astronauts have to work long time under stressed conditions in space environment. It has been reported that working more than 48–56 h a week is considered potentially harmful [14], [15]. Working more than 70 h a week accompanied with physical and mental stress demanding job assignment is supposed to result in fatigue, which further on effects health of astronaut and can result in failure of space exploration mission. To investigate the possible effects of this leadership responsibility and long duration working hours on cognitive performance and sleepiness using questionnaires, salivary cortisol levels, heart rate variability, muscular fatigue, sleep monitoring, and neuro-behavioral tests, this study was planned. Extreme environments allow us to examine various aspects of the psycho-physiological relationship that is essential to fully understand the concept of adaptation of humans to the stressful conditions and long duration of working hours to comply with planned experiments in these environments [8]. When crew teams or individuals operate in extreme environments, their responses are more purely a product of either situational drivers or internal personal characteristics. The MDRS, Utah (USA) provides a unique opportunity to examine the interaction of salient individual factors such as gender and personality factors on social relationships and group identity. The Mars Desert Research Station (MDRS) is an analog to a Mars surface habitat, constructed for mission simulations according to Mars Reference Mission guidelines [8], and located in a US southwest desert region relevant to Mars analog geology, human factors and biology research. MDRS includes an upper deck with six private staterooms having personal storage and desks, a galley area, workstations, and meeting/eating area, plus a lower deck with a laboratory, toilet, shower, and extra-vehicular activity (EVA) preparation rooms.Materials and methodsThe 30 members were selected from five crews. Among them, 10 crew members (Commander:Executive officer; 5:5) and 20 crew members (Chief scientist:Geologist:Crew engineer:Journalist:Health and safety officer; 6:5:1:4:5) were divided into leadership and normal team, respectively. The ages for the leadership aged 20–26 (23.6 (2.4)) while normal crew ranged from 21 to 25 (23.5 (2.5) years). All of the crew members gave their written informed consent to participate. Crew structure and responsibilities of different crew members has been described in Table 1. Confined and isolated environment, international crew members from different cultures, challenges to meet physical demands (working in suits, science experiments, extravehicular activities Fig. 1, Fig. 2, Fig. 3, Fig. 4, Fig. 5) as well as unavoidable Hab environmental characteristics (noise, isolation, confinement, low habitable volume per person, and limited opportunities for variety and change) was faced by all crew members. The both groups were tested on days 1 (first day of mission), 7 (mid-of mission), and 14 days (end of mission). Karolinska Sleepiness Scale 5-point scale ((i) very alert, (ii) alert, (iii) neither alert nor sleepy, (iv) sleepy, no difficulty remaining awake, and (v) extremely sleepy, fighting sleep) was used for sleep analysis [1]. Physiological and mental fatigue symptom ratings were analyzed by 11 items [3]. The neuro-behavioral tests were analyzed using WAIS-R Digit Symbol substitution test; APT two-choice visual reaction time and APT k test [3], [16], [11], [9]. Maximum heart rate was calculated [5]. Saliva was collected using the Saliva Collection System (Greiner Bio-One GmbH, Kremsmunster, Austria), according to the manufacturer's instructions. Smoking, eating and drinking were not permitted 30 min prior to collection. Saliva samples were collected in morning between 0800 and 0820 on 1 (first day of mission), 7 (mid-of mission), and 14 days (end of mission) and immediately stored at −4 °C. The analysis of salivary cortisol was performed using the RIA technique [7]. Data were analyzed using SPSS (SPSS Inc.; Chicago, IL, USA).

Section snippets

Results

Mean working hours of leadership group [80 (13)] was significantly higher as compared to normal group [60 (11)] hours per week (p < 0.005). KSS score were significantly lower in leadership team [2.45 (SD 1.34)] as compared to normal team [5.23 (SD 1.89)] (p < 0.05). Fatigue index score was significantly lower in leadership team as compared to normal team (p < 0.01, Table 2).There was typically no group difference for performance development between days 1, 7 and end day of mission. Only one

Discussion

The working hours of leadership group were significantly higher as compared to normal group. It might be due to more responsibility and more workload. This study reported that increasing symptoms of fatigue and sleepiness did not affect the performance, i.e. neuro-behavior in leadership group as compared to normal group. The leadership group had the fastest reaction times on 14th day (end of mission) as compared to first and mid of mission. It might be due to more learning effects as supported

Acknowledgement

We would like to express gratitude towards the Mars Society, ILEWG, ESA/ESTEC, l’Ecole de l’Air, Prof. Bernard Foing, Dr. Guy Pignolet from the SALM institute, Mr. Akos Kerezturi, Dr. Tamarack Czarnik, Dr Carol Stoker (NASA Ames), the Mission Support, Mr. Don Lusko and all other related people for their daily assistance and our remote supporters from America, Europe, Canada and JBR research group India. We are thankful to Mag. Michaela Neuhofer (Product Manager Saliva Systems, Clinical Research

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