Impact of 2 days of staging at 2500–4300 m on sleep quality and quantity following subsequent exposure to 4300 m

Abstract

The impact of 2 days of staging at 2500–4300 m on sleep quality and quantity following subsequent exposure to 4300 m was determined. Forty‐eight unacclimatized men and women were randomly assigned to stage for 2 days at one of four altitudes (2500, 3000, 3500, or 4300 m) prior to assessment on the summit of Pikes Peak (4300 m) for 2 days. Volunteers slept for one night at sea level (SL), two nights at respective staging altitudes, and two nights at Pikes Peak. Each wore a pulse oximeter to measure sleep arterial oxygen saturation (sSpO2, %) and number of desaturations (DeSHr, events/hr) and a wrist motion detector to estimate sleep awakenings (Awak, awakes/hr) and sleep efficiency (Eff, %). Acute mountain sickness (AMS) was assessed using the Environmental Symptoms Questionnaire and daytime SpO2 was assessed after AMS measurements. The mean of all variables for both staging days (STG) and Pikes Peak days (PP) was calculated. The sSpO2 and daytime SpO2 decreased (p < 0.05) from SL during STG in all groups in a dose‐dependent manner. During STG, DeSHr were higher (p < 0.05), Eff was lower (p < 0.05), and AMS symptoms were higher (p < 0.05) in the 3500 and 4300 m groups compared to the 2500 and 3000 m groups while Awak did not differ (p > 0.05) between groups. At PP, the sSpO2, DeSHr, Awak, and Eff were similar among all groups but the 2500 m group had greater AMS symptoms (p < 0.05) than the other groups. Two days of staging at 2500–4300 m induced a similar degree of sleep acclimatization during subsequent ascent to 4300 m but the 2500 m group was not protected against AMS at 4300 m.

Wilderness Medical Society Clinical Practice Guidelines for the Prevention, Diagnosis, and Treatment of Acute Altitude Illness: 2024 Update

“…of preventing acute altitude illness. [17][18][19][20] In planning the rate of ascent, the altitude at which someone sleeps is considered more important than the altitude reached during waking hours.…”

“…Staged Ascent and Preacclimatization. Two studies showed that spending 6 to 7 d at moderate altitude (∼2200−3000 m) prior to proceeding to higher altitude (referred to as "staged ascent") decreases the risk of AMS, improves ventilation and oxygenation, and blunts the pulmonary artery pressure response following subsequent ascent to 4300 m. 19,58 A more recent study has shown that a 2-d stay at 3000 m is also effective at preventing AMS upon further ascent to 4300 m. 20 Many travelers to high altitude visit mountain resorts at more moderate elevations between 2500 and 3000 m. The value of short stays at intermediate elevations of ∼1500 m for decreasing the risk of AMS with such ascents makes sense from a physiologic standpoint, but aside from a cross-sectional study showing a decreased risk of AMS in travelers to resort communities between 1920 and 2950 m when they spent 1 night at 1600 m prior to ascent, 6 this approach has not been studied in a prospective randomized fashion.…”

“…Controlling the rate of ascent, in terms of the number of meters gained per day, is a highly effective means of preventing acute altitude illness. 17-20 In planning the rate of ascent, the altitude at which someone sleeps is considered more important than the altitude reached during waking hours.…”