title: Sleep at high altitude: guesses and facts.
abstract: Lowlanders commonly report a poor sleep quality during the first few nights after arriving at high altitude. Polysomnographic studies reveal that reductions in slow wave sleep are the most consistent altitude-induced changes in sleep structure identified by visual scoring. Quantitative spectral analyses of the sleep electroencephalogram have confirmed an altitude-related reduction in the low-frequency power (0.8-4.6 Hz). Although some studies suggest an increase in arousals from sleep at high altitude, this is not a consistent finding. Whether sleep instability at high altitude is triggered by periodic breathing or vice versa is still uncertain. Overnight changes in slow wave-derived encephalographic measures of neuronal synchronization in healthy subjects were less pronounced at moderately high (2,590 m) compared with low altitude (490 m), and this was associated with a decline in sleep-related memory consolidation. Correspondingly, exacerbation of breathing and sleep disturbances experienced by lowlanders with obstructive sleep apnea during a stay at 2,590 m was associated with poor performance in driving simulator tests. These findings suggest that altitude-related alterations in sleep may adversely affect daytime performance. Despite recent advances in our understanding of sleep at altitude, further research is required to better establish the role of gender and age in alterations of sleep at different altitudes, to determine the influence of acclimatization and of altitude-related illness, and to uncover the characteristics of sleep in highlanders that may serve as a study paradigm of sleep in patients exposed to chronic hypoxia due to cardiorespiratory disease.
authors.affiliation: Sleep Disorders Center, Pulmonary Division, University Hospital of Zurich, Zurich; Switzerland; Zurich Center for Human Integrative Physiology, University of Zurich, Zurich, Switzerland; and Zurich Center for Interdisciplinary Sleep Research, University of Zurich, Zurich, Switzerland konrad.bloch@usz.ch.
authors.forename: Konrad E
authors.initials: KE
authors.lastname: Bloch
authors.affiliation: Sleep Disorders Center, Pulmonary Division, University Hospital of Zurich, Zurich; Switzerland;
authors.forename: Jana C
authors.initials: JC
authors.lastname: Buenzli
authors.affiliation: Sleep Disorders Center, Pulmonary Division, University Hospital of Zurich, Zurich; Switzerland; Zurich Center for Interdisciplinary Sleep Research, University of Zurich, Zurich, Switzerland.
authors.forename: Tsogyal D
authors.initials: TD
authors.lastname: Latshang
authors.affiliation: Sleep Disorders Center, Pulmonary Division, University Hospital of Zurich, Zurich; Switzerland; Zurich Center for Human Integrative Physiology, University of Zurich, Zurich, Switzerland; and.
authors.forename: Silvia
authors.initials: S
authors.lastname: Ulrich
mesh_terms: D000531:Altitude; D000818:Animals; D006801:Humans; D000860:Hypoxia / Q000209:etiology / Q000503:physiopathology; D012890:Sleep / Q000502:physiology*; D007319:Sleep Initiation and Maintenance Disorders / Q000209:etiology / Q000503:physiopathology / Q000523:psychology
keywords: altitude; hypoxia; insomnia; sleep