0243 SLEEP REGULARITY AND MENTAL HEALTH DURING EXTENDED ANTARCTIC RESIDENCE

Abstract

Abstract Introduction As humans’ advance towards a Mars mission, ensuring astronaut safety, well-being, and performance becomes increasingly critical. Long-duration space exploration presents several challenges for human sleep, including altered photoperiods, prolonged confinement, and monotony. Antarctica provides an ideal analog for understanding how these and other stressors impact sleep over time. Prior studies among Antarctic cohorts have found reduced total sleep, increased sleep onset, and circadian phase delay. However, day-to-day regularity of sleep-wake patterns in the Antarctic over prolonged periods has not been studied. Methods Crew members (N= 110) at a coastal (McMurdo: MM, n = 88) and an inland Antarctic station (South Pole: SP, n = 22) were studied longitudinally for up to 9-months. Sleep was monitored continuously with actigraphy (Actiwatch Spectrum, Philips Respironics) and examined in relation to cumulative time on station and calendar month (photoperiod). Self-reported mental health symptoms were also examined monthly using The Mental Health Checklist (MHCL). The Sleep Regularity Index (SRI; Phillips et al., 2017) which calculates the percentage probability of an individual being in the same state (sleep vs. wake) at any two time-points 24 hours apart was calculated to examine sleep regularity over time. Results Controlling for time on station prior to participation, we observed no significant changes in monthly SRI over a 6-month period at MM where photoperiod alterations are less extreme. At SP, SRI remained very stable during months of total daylight but declined during winter months in the absence of sunlight. SRI scores were significantly different between month-8 and month-9 and with large effect sizes across month-7, month-8, and month-9. Participants with lower month-7 SRI scores had significantly higher MHCL poor self-regulation scores at the end of the mission. Conclusion Day-to-day variability in sleep–wake patterns is an important predictor of health and safety. Our findings show reductions in sleep regularity during prolonged Antarctic residence particularly at the SP station, where sunlight is absent for 6 months of the year. Less sleep regularity predicted worse mental health functioning. These findings suggest that mitigation the impact of altered light-dark cycles on sleep is critical for a Mars mission. Support (if any) NASA award #NNX15AC13G S014 to the last author.