Traveling to elevations of 8,000 feet (2,400 meters) and above often introduces a challenge that many visitors do not anticipate: disrupted sleep. Restless nights, frequent awakenings, and feeling unrefreshed upon waking are common experiences for lowlanders ascending to high altitude. This sleep disturbance is not merely a matter of an unfamiliar bed; it is a direct physiological consequence of the thinner air. Understanding the science behind this poor sleep and taking proactive steps can greatly enhance both safety and enjoyment during a high-altitude trip.
Understanding Altitude’s Effect on Sleep
The primary culprit behind poor sleep at high elevations is the reduced availability of oxygen, known as hypoxia. This lower oxygen concentration triggers physiological responses designed to compensate, which interferes with normal sleep patterns. The most notable effect is the development of periodic breathing, or Cheyne-Stokes respiration.
Periodic breathing involves a cycle of rapid, deep breaths followed by a noticeable pause (apnea) lasting several seconds. This pause causes a drop in blood oxygen levels, stimulating the brain to wake the sleeper just enough to gasp for air and restart the cycle. This process causes frequent, brief arousals throughout the night, leading to fragmented sleep, even if the sleeper does not remember waking up.
The overall architecture of sleep also changes at altitude. Studies show a shift toward lighter sleep stages, with a decrease in restorative slow-wave sleep and rapid eye movement (REM) sleep. Oxygen deprivation is most severe during sleep, forcing the body to work harder to maintain saturation levels, which contributes to feeling unrested.
Acclimation and Preventative Measures
The most effective preventative measure against altitude-related sleep disruption and illness is a gradual ascent. Travelers planning to sleep above 9,850 feet (3,000 meters) should limit the increase in sleeping altitude to no more than 1,600 feet (500 meters) per day. Schedule a rest day for every 3,300 feet (1,000 meters) of elevation gain to allow the body to acclimatize.
Maintaining proper hydration throughout the day is important, as the dry mountain air causes moisture loss with every breath. Adequate water intake helps the body adjust more smoothly; urine should remain light yellow or clear as a sign of sufficient fluid consumption.
Avoid heavy meals, particularly late at night. The digestive process can divert energy and oxygen away from the respiratory system, making nighttime breathing more labored.
For those unable to follow a gradual ascent schedule, a doctor may recommend prophylactic medication such as Acetazolamide. This medication works by increasing the body’s breathing drive, which reduces the severity of periodic breathing and improves oxygen saturation during sleep. A typical preventative dosage is 125 mg taken twice daily, starting the day before ascent. Consult with a healthcare professional before taking this prescription drug.
Immediate Sleep Improvement Techniques
Once at altitude, several techniques can manage fragmented sleep. One simple physical adjustment is to elevate the head of the bed by 6 to 12 inches, perhaps by propping it up with extra pillows. Sleeping slightly upright can help reduce the frequency and severity of periodic breathing episodes by improving oxygen flow and making breathing easier.
Maintaining excellent sleep hygiene involves ensuring the sleeping area is dark, quiet, and cool. Avoiding screen time in the hour before bed helps signal the brain that it is time to rest. Travelers should also avoid substances like alcohol and sedatives, which depress the respiratory drive and can worsen the hypoxia and periodic breathing that occur during sleep.
In cases where sleep disruption is severe, supplemental oxygen may be available. Breathing higher concentrations of oxygen directly addresses the root cause of the sleep disturbance and can quickly resolve the periodic breathing cycle. While not always practical or available, it is highly effective for improving sleep quality at high altitude.
Recognizing Severe Altitude Sickness
While most sleep disturbances at altitude are manageable, they can occasionally warn of a more serious condition. Acute Mountain Sickness (AMS) often presents with a persistent headache, nausea, and severe fatigue, which further interfere with sleep. If symptoms worsen despite resting at the same altitude, descent is mandatory.
More dangerous are High Altitude Cerebral Edema (HACE) and High Altitude Pulmonary Edema (HAPE). HACE, which involves brain swelling, is indicated by confusion, loss of coordination, and irrational behavior. HAPE, which involves fluid in the lungs, is signaled by a persistent dry cough, shortness of breath even at rest, and sometimes a cough that produces pink or frothy sputum. The appearance of any signs of HACE or HAPE requires immediate descent and urgent medical attention.