Although some studies have identified changes to the structure and the quality of sleep at high altitudes, there was actually little in the way of objective evidence to suggest that altitude has a negative impact on sleep. This led researchers to undertake a scientific review that was published by the American Physiological Society in 2015.
Insomnia from a recent change in altitude
Researchers found that sleep disturbances in those who recently moved to a high altitude were common when measured by questionnaires. In one study, close to half of the tourists surveyed at a ski resort located roughly 11,500 feet above sea level reported disturbed sleep and frequent awakenings during the first night at their hotel.
Objective sleep changes were covered in one study that measured sleep through the use of polysomnographic sleep studies. No significant changes were found in sleep efficiency or awakenings after travelling from 1,500 feet to 5,300 feet and then on to 8,500 feet but researchers did record a slight reduction in deep sleep.
The review identified a study that suggested the higher the altitude, the bigger the impact on sleep. In that study, mountaineers who reached an altitude of 15,000 feet experienced more subjective insomnia and a reduction in deep sleep compared to lower altitudes.
Why does altitude affect sleep?
As altitude increases, oxygen levels in the air decrease. The review’s authors pointed out that earlier studies have linked sleep fragmentation at altitude with oxygen deprivation — but more recent studies have found less of a link between the frequency of awakenings and high altitude.
Researchers suggested that subtle changes in electrical brain activity due to mild oxygen deprivation may affect brain function and this could explain any subsequent impact on sleep. In fact, two studies included in the review found that when participants suffering from cognitive impairment at higher altitude were given supplemental oxygen at night, daytime performance improved.
The authors of the review pointed out that the symptoms of altitude sickness such as headaches, coughs, and shortness of breath may also interfere with sleep quality — but there was little evidence to support this theory.
How long does it take for sleep to improve at altitude?
Although researchers pointed out that there was very scant research regarding sleep and altitude acclimatization, one study found that sleep was partially normalized by the third night — but this depended on the altitude.
The review identified periodic breathing as one aspect of sleep that appears to be affected by exposure to high altitudes. Periodic breathing (also known as apnea and hypopnea events) is typically associated with sleep apnea and with drops in blood oxygen levels.
At lower altitudes (below 11,000 feet) periodic breathing improved by the second night. At higher altitudes (15,000 feet and above), periodic breathing actually increased for each night spent at altitude.
Sleeping pills for altitude related insomnia
The review identified one study that found zolpidem (Ambien and other brands) provided minor but statistically significant improvements in deep sleep at simulated altitudes of up to 13,000 feet.
Another study on climbers staying at Everest base camp (roughly 17,000 feet above sea level) found that temazepam (Restoril) improved subjective sleep quality — but in a study on trekkers at 16,000 feet in Nepal, the drug was no better than a placebo at improving subjective insomnia.
It’s clear that although sleep does appear to be affected by altitude, more studies are needed to determine why this is the case. Although there are many anecdotal stories of sleep being more difficult at altitude, your sleep should return to normal once your body acclimatizes or when you return home.