Sleep during an Antarctic overwintering: comparing an altitude base and a coastal station

Introduction

The occurrence of sleep disturbances in Antarctic regions is a consistent finding in literature. Indeed, spending winter in Antarctica, exposed to total darkness, has been significantly associated with total hours of sleep, duration of the longest sleep event, time of sleep onset and quality of sleep. Considering the importance of light as a Zeitgeber, and the major role of the circadian rhythm in sleep-wake regulation, this hardly comes as a surprise. However, less is known about the potential side effect of the chronic exposure to hypobaric hypoxia, as experienced in stations at altitude, on these results. In the present study, we compared two different campaigns (winter and summer) over two different research station (Concordia – corrected altitude 3800 m and Dumont d’Urville – sea level).

Materials and methods

To do so, 24 h actigraphy recordings were collected over 8 expeditioners in Concordia and 16 expeditioners in Dumont d’Urville during winter and summer.

Results

The results showed that during the day time no differences were observed in the time spent to work (p = 0.16), in the energy expenditure (p = 0.066) and in the number of steps (p = .144). This indicates quite similar settings in terms of the generation of homeostatic sleep pressure due to physical activity. However, comparing both settings for night time yielded a significant group effect for the total sleep time (DDU Concordia; p = 0.036), the sleep efficiency (DDU Concordia; p = 0.035) and the wake after sleep onset (WASO) (DDU Concordia; p = 0.006). Moreover, a significant session effect was observed for the fragmentation of sleep (summer winter; p = 0.003). All other parameters analyzed such as total sleep time? (F 1), energy expenditure (F 1), time in bed (F 1), sleep onset (F 1) remained non-significant.

Conclusion

Our results show that the main differences in sleep parameters were associated to the effect of altitude and that seasonality only affected the fragmentation of sleep. We can thus conclude that the altitude parameter needs to be more carefully taken into account in the future investigation of sleep in extreme environment.

Acknowledgements

This work was financially supported by ESA/Prodex and Institut Paul-Emile Victor (IPEV). The authors are grateful to all participants.