Sleep disordered breathing and acute mountain sickness in workers rapidly transported to the South Pole (2835 m).

BACKGROUND

Sleep disordered breathing may be a risk factor for high altitude illness. Past Antarctic sleep studies suggest that rapid transport from sea level (SL) to the Amundsen Scott South Pole Station (SP, 2835 m) increases risk of Acute Mountain Sickness (AMS). We analyzed sleep studies in 38 healthy polar workers to explore the association between sleep disordered breathing and AMS after rapid transport to the South Pole.

METHODS

Subjects completed a baseline questionnaire, performed basic physiology tests, and were evaluated for AMS and medication use using an extended Lake Louise Questionnaire (LLQ) during their first week at the South Pole. Participants were included in this study if they took no medications and underwent polysomnography on their first nights at Sea Level and the South Pole using the Vivometrics LifeShirt(®). Within group changes were assessed with Wilcoxon signed rank tests and between group differences were assessed with Kruskal-Wallis rank sum tests.

RESULTS

Overall, 21/38 subjects met criteria for AMS at some time on or prior to the third morning at the South Pole. Subjective poor sleep quality was reported by both AMS (65%) and no AMS (41%) groups. The Apnea Hypopnea Index (AHI) increased significantly in both the AMS and no AMS groups, but the difference in the increase between the two groups was not statistically significant. Increased AHI was not associated with increased AMS symptoms. Previous altitude illness (p=0.06) and residence at low altitudes (p = 0.02) were risk factors for AMS.

CONCLUSION

AMS was not significantly associated with sleep architecture changes or increased AHI. However, AHI sharply increased at South Pole (19/38 participants) primarily due to central apneas. Those developing AMS were more likely to have experienced previous problems at altitude and reported living at lowland altitudes within the 3 months prior to rapid transport to the South Pole than those without AMS.