Sleep at Altitude

Reported Sleep Disturbances

Many travelers report a decrease of quality of sleep when traveling from sea-level to high altitudes. Newcomers to altitude typically describe trouble falling asleep and frequent wakings throughout the night.7 One study determined that 46% of 100 Iranian ski tourists reported frequent awakenings and other sleep disturbances such as insomnia during their first night sleeping at 3,500 m.5,7 Another study analyzed data from reports of 305 Chinese soldiers transported from 500 m to 3,700 m in Lhasa and found similar results. Approximately, 32% of the soldiers reported insomnia in the first night at altitude and 74% of 246 workers who were air-lifted to the South Pole at 2,835 m reported difficulty falling and staying asleep throughout the first week.1

Change in Breathing Pattern

Many theories state that the “periodic breathing pattern,” common during sleep at high altitude, is a potential cause of sleep disturbances. Periodic breathing is a form of Cheyne-Stokes respiration and reflects changes in neural signaling due to hypoxia and alkalosis during sleep.4 Hypoxia is a respiratory stimulant while alkalosis is a respiratory depressant.4 This mixed signaling is the source of the altered breathing during non-REM sleep encountered at altitudes over 2500 m. The frequency of periodic breathing during sleep increases as the altitude increases.3,4,7

Decreased Sleep Efficiency 

Compared with sea level, several studies have depicted that sleep at higher altitude is characterized by decreased sleep efficiency, prolonged superficial stages of sleep, and reduced stages of deep sleep.12 The image below is a qualitative representation of sleep structure recorded at sea level and at high altitude. The area encircled by the outer line reflects the time in bed and the area of the shaded inner pie chart the time asleep.7,13 The fractions of superficial stages of sleep are symbolized by “NR1&2,” the fractions of deep non-rapid eye movement sleep are represented by “NR3&4,” and the stages of  rapid eye movement sleep are exemplified by “REM.”

Fig. 1. Depicts a qualitative comparison of sleep quality at sea level vs. altitude > 1,500 m13

Shift in Brain Waves 

Everyone is aware of the importance of quality of sleep when it comes to memory processing. One study has associated a decline in sleep-related memory consolidation with the decrease in slow wave-derived encephalographic measures of neuronal synchronization in healthy subjects observed overnight at high altitude.15  Another study by Stadelmann et al. discovered that quantitative spectral analysis of frontal and central EEG derivations reflected an altitude-dependent decrease in slow wave activity.14

Daytime Performance

A study, analyzing sleep disturbances experienced by lowlanders with obstructive sleep apnea during a stay at 2,590 m, discusses the association between sleep disturbances with poor performance in driving simulator tests.11 Studies performed at altitudes of 3800-3900 have revealed that supplementing with nocturnal oxygen improves daytime performance in neuropsychological tests, increases overall sleep quality, and reduces the occurrence of periodic breathing. 9,10 Although further studies are needed, the stated findings suggest that altitude-related alterations in sleep may negatively affect overall daytime performance.7

Can We Acclimate to High Altitude? 

Over time, research points to some sort of acclimation concerning sleep at high altitude; although research analyzing acclimation is very limited. Studies analyzing altitudes between 4,5559 m to 6,835 m have determined that the frequency of periodic breathing increased with the time spent at high altitude altitude.2,12 Opposingly, in studies at lower altitudes such as 1,650 m, 2,590 m and 3,450 m, periodic breathing decreased from the first to the second night.6,8 These observations suggest that there is an altitude-dependent effect of acclimatization on sleep structure. Interestingly, the same study that determined an increase in periodic breathing with time spent at an altitude of 4,559 also noted a decrease in arousal index and normalization of nocturnal oxygen saturation with increased time spent at high altitude.12 Stadelmann et al. determined that there was a statistically significant increase in the number of sleep cycles at higher altitudes with the longer the stay at altitude.14

Dr. Ebert-Santos’s Decision to Continue the Research

Despite recent advances in our understanding of sleep at high altitude, further research is needed to understand how demographics may alter sleep at high altitude, to determine the process of sleep-acclimatization, and to uncover the characteristics of sleep in local-highlanders.7 Dr. Ebert- Santos continues to be an advocate for the Summit County community regarding the effects of high altitude on health and has decided to pursue a study researching the effects of altitude on oxygen saturation during sleep of adults ranging from the ages 25-65 years old. Stay tuned for her process, her results, and her conclusions! 

Caroline, PA-S

References:

  1. Anderson PJ, Wiste HJ, Ostby SA, Miller AD, Ceridon ML, Johnson BD. Sleep disordered breathing and acute mountain sickness in workers rapidly transported to the South Pole (2835m). Respir Physiol Neurobiol 210: 38–43, 2015.
  2. Bloch KE, Latshang TD, Turk AJ, Hess T, Hefti U, Merz TM, Bosch MM, Barthelmes D, Hefti JP, Maggiorini M, Schoch OD. Nocturnal periodic breathing during acclimatization at very high altitude at Mount Muztagh Ata (7,546 m). Am J Respir Crit Care Med 182: 562–568, 2010.
  3. Erba P, Anastasi S, Senn O, Maggiorini M, Bloch KE. Acute mountain sickness is related to nocturnal hypoxemia but not to hypoventilation. Eur Respir J 24: 303–308, 2004.
  4. Gallagher, Scot A. High altitude illness: Physiology, risk factors, and general prevention.  Up-to-date.Waltham, Mass.: UpToDate; September 20, 2017. www.uptodate.com. Accessed March 20, 2019.
  5. Jafarian S, Gorouhi F, Taghva A, Lotfi J. High-altitude sleep disturbance: results of the Groningen Sleep Quality Questionnaire survey. Sleep Med 9: 446–449, 2008.
  6. Kohler M, Kriemler S, Wilhelm EM, Brunner-Larocca H, Zehnder M, Bloch KE. Children at high altitude have less nocturnal periodic breathing than adults. Eur Respir J 32: 189–197, 2008.
  7. Konrad E. Bloch, Jana C. Buenzil, Tsogyal D. Latshang, and Silvia Ulrich. Sleep at high altitude: guesses and facts. Journal of Applied Physiology 2015 119:12, 1466-1480. 
  8. Latshang TD, Lo Cascio CM, Stowhas AC, Grimm M, Stadelmann K, Tesler N, Achermann P, Huber R, Kohler M, Bloch KE. Are nocturnal breathing, sleep, and cognitive performance impaired at moderate altitude (1,630–2,590 m)? Sleep 36: 1969–1976, 2013.
  9. Li P, Zhang G, You HY, Zheng R, Gao YQ. Training-dependent cognitive advantage is suppressed at high altitude. Physiol Behav 106: 439–445, 2012.
  10. Luks AM, van MH, Batarse RR, Powell FL, Grant I, West JB. Room oxygen enrichment improves sleep and subsequent day-time performance at high altitude. Respir Physiol 113: 247–258, 1998.
  11. Nussbaumer-Ochsner Y, Schuepfer N, Ulrich S, Bloch KE. Exacerbation of sleep apnoea by frequent central events in patients with the obstructive sleep apnoea syndrome at altitude: a randomised trial. Thorax 65: 429–435, 2010.
  12. Nussbaumer-Ochsner Y, Ursprung J, Siebenmann C, Maggiorini M, Bloch KE. Effect of short-term acclimatization to high altitude on sleep and nocturnal breathing. Sleep 35: 419–423, 2012.
  13. Rechtschaffen A, Kales A. A Manual of Standardized Terminology, Techniques and Scoring System for Sleep Stages of Human Subjects. Washington, DC: Public Health Service, US Government Printing Office, 1968.
  14. Stadelmann K, Latshang TD, Lo Cascio CM, Tesler N, Stoewhas AC, Kohler M, Bloch KE, Huber R, Achermann P. Quantitative changes in the sleep EEG at moderate altitude (1630 m and 2590 m). PLoS One 8: e76945, 2013.
  15. Tesler N, Latshang TD, Lo Cascio CM, Stadelmann K, Stoewhas AC, Kohler M, Bloch KE, Achermann P, Huber R. Ascent to moderate altitude impairs overnight memory improvements. Physiol Behav 139: 121–126, 2015.