Sleeping with elevated upper body does not attenuate acute mountain sickness - pragmatic randomized clinical trial

Abstract Purpose Acute mountain sickness commonly occurs following ascent to high altitude and is aggravated following sleep. Cephalad fluid shifts have been implicated. We hypothesized that sleeping with the upper body elevated by 30°, reduces the risk of acute mountain sickness. Methods In a pragmatic, randomized, observer-blinded field study at 4,554 meters altitude, we investigated 134 adults aged 18–70 years with a Lake Louise score (LLS) between 3 and 12 points at the evening of their arrival at the altitude. The individuals were exposed to sleeping on an inflatable cushion elevating the upper body by 30° or on a sham pillow in a horizontal position. The primary endpoint was the change in the Acute Mountain Sickness-Cerebral (AMS-C) score in the morning after sleeping at an altitude of 4,554 meters compared with the evening before. Sleep efficiency was the secondary endpoint. Results Among 219 eligible mountaineers, 134 fulfilled the inclusion criteria and were randomized. The AMS-C score increased by 0.250±0.575 in the control group and by 0.121±0.679 in the intervention group (difference 0.105, 95% CI -0.098 – 0.308, p = 0.308). Oxygen saturation in the morning was 79±6 % in the intervention group and 78±6 % in the control group (p=0.863). Sleep efficiency did not differ between groups (p=0.115). Conclusions Sleeping with the upper body elevated by 30° does not lead to relevant reductions in acute mountain sickness symptoms or hypoxemia at high altitude.