title: Are nocturnal breathing, sleep, and cognitive performance impaired at moderate altitude (1,630-2,590 m)?
abstract: OBJECTIVE
  Newcomers at high altitude (> 3,000 m) experience periodic breathing, sleep disturbances, and impaired cognitive performance. Whether similar adverse effects occur at lower elevations is uncertain, although numerous lowlanders travel to moderate altitude for professional or recreational activities. We evaluated the hypothesis that nocturnal breathing, sleep, and cognitive performance of lowlanders are impaired at moderate altitude.
  
  
  METHODS
  Randomized crossover trial.
  
  
  METHODS
  University hospital at 490 m, Swiss mountain villages at 1,630 m and 2,590 m.
  
  
  METHODS
  Fifty-one healthy men, median (quartiles) age 24 y (20-28 y), living below 800 m.
  
  
  METHODS
  Studies at Zurich (490 m) and during 4 consecutive days at 1,630 m and 2,590 m, respectively, 2 days each. The order of altitude exposure was randomized. Polysomnography, psychomotor vigilance tests (PVT), the number back test, several other tests of cognitive performance, and questionnaires were evaluated.
  
  
  RESULTS
  The median (quartiles) apnea-hypopnea index at 490 m was 4.6/h (2.3; 7.9), values at 1,630 and 2,590 m, day 1 and 2, respectively, were 7.0/h (4.1; 12.6), 5.4/h (3.5; 10.5), 13.1/h (6.7; 32.1), and 8.0/h (4.4; 23.1); corresponding values of mean nocturnal oxygen saturation were 96% (95; 96), 94% (93; 95), 94% (93; 95), 90% (89; 91), 91% (90; 92), P < 0.05 versus 490 m, all instances. Slow wave sleep on the first night at 2,590 m was 21% (18; 25) versus 24% (20; 27) at 490 m (P < 0.05). Psychomotor vigilance and various other measures of cognitive performance did not change significantly.
  
  
  CONCLUSIONS
  Healthy men acutely exposed during 4 days to hypoxemia at 1,630 m and 2,590 m reveal a considerable amount of periodic breathing and sleep disturbances. However, no significant effects on psychomotor reaction speed or cognitive performance were observed.
  
  
  BACKGROUND
  Clinicaltrials.gov: NCT01130948.
authors.affiliation: Sleep Disorders Center and Pulmonary Division, University Hospital Zurich.
authors.forename: Tsogyal D
authors.initials: TD
authors.lastname: Latshang
authors.forename: Christian M
authors.initials: CM
authors.lastname: Lo Cascio
authors.forename: Anne-Christin
authors.initials: AC
authors.lastname: Stöwhas
authors.forename: Mirjam
authors.initials: M
authors.lastname: Grimm
authors.forename: Katrin
authors.initials: K
authors.lastname: Stadelmann
authors.forename: Noemi
authors.initials: N
authors.lastname: Tesler
authors.forename: Peter
authors.initials: P
authors.lastname: Achermann
authors.forename: Reto
authors.initials: R
authors.lastname: Huber
authors.forename: Malcolm
authors.initials: M
authors.lastname: Kohler
authors.forename: Konrad E
authors.initials: KE
authors.lastname: Bloch
mesh_terms: D000328:Adult; D000531:Altitude; D001143:Arousal / Q000502:physiology; D003071:Cognition / Q000502:physiology*; D018592:Cross-Over Studies; D006801:Humans; D008297:Male; D009483:Neuropsychological Tests; D017286:Polysomnography; D012143:Respiratory Physiological Phenomena; D012890:Sleep / Q000502:physiology*; D012891:Sleep Apnea Syndromes / Q000209:etiology; D012893:Sleep Wake Disorders / Q000209:etiology; D011795:Surveys and Questionnaires; D055815:Young Adult
keywords: Altitude; healthy; hypoxia; sleep apnea; vigilance