The effect of zolpidem on cognitive function and postural control at high altitude

Sleep. 2018 Oct 1;41(10). doi: 10.1093/sleep/zsy153.


Study objectives: Sleep is altered at high altitude leading many mountaineers to use hypnotics in order to improve sleep efficiency. While after a full night at altitude the short-acting hypnotic zolpidem does not appear to alter cognitive function, residual adverse effects should be considered following early waking-up as performed by mountaineers. We hypothesized that zolpidem intake at high altitude would alter cognitive function 4 hours after drug intake.

Methods: In a randomized double-blind controlled cross-over study, 22 participants were evaluated during two nights at sea level and two nights at 3800 m, 4 hours after zolpidem (10 mg) or placebo intake at 10:00 pm. Polygraphic recording was performed until waking-up at 01:30 am. Sleep quality, sleepiness and symptoms of acute mountain sickness were assessed by questionnaires. Two cognitive tasks (Simon task and duration-production task) were performed at rest and during exercise and postural control was evaluated.

Results: Zolpidem increased reaction time in all conditions (zolpidem 407 ± 9 ms vs. placebo 380 ± 11 ms; p < 0.001) and error rate in incongruent trials only (10.2 ± 1.1% vs. 7.8 ± 0.8%; p < 0.01) in the Simon task and increased time perception variability (p < 0.001). Zolpidem also altered postural parameters (e.g. center of pressure area, zolpidem 236 ± 171.5 mm2 vs. placebo 119.6 ± 59 mm2; p < 0.001). Zolpidem did not affect apnea-hypopnea index and mean arterial oxygen saturation (p > 0.05) but increased sleep quality (p < 0.001). Zolpidem increased symptoms of acute mountain sickness and sleepiness (p < 0.05).

Conclusions: Acute zolpidem intake at high altitude alters cognitive functions and postural control during early wakening which may be deleterious for safety and performances of climbers.

Publication types

  • Randomized Controlled Trial
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Altitude Sickness / chemically induced
  • Altitude Sickness / epidemiology
  • Altitude*
  • Cognition / drug effects*
  • Cross-Over Studies
  • Disorders of Excessive Somnolence / drug therapy
  • Double-Blind Method
  • Female
  • Humans
  • Male
  • Placebos
  • Posture / physiology*
  • Pyridines / administration & dosage
  • Reaction Time / drug effects
  • Sleep / drug effects
  • Sleep Aids, Pharmaceutical*
  • Sleep Initiation and Maintenance Disorders / drug therapy*
  • Sleepiness
  • Wakefulness / drug effects
  • Zolpidem / administration & dosage
  • Zolpidem / adverse effects*


  • Placebos
  • Pyridines
  • Sleep Aids, Pharmaceutical
  • Zolpidem