“…11,12 Nevertheless, it has not been conclusively studied whether healthy mountain travelers experience nocturnal breathing and sleep disturbances already at moderate altitude (< 3,000 m) and whether this is associated with cognitive impairments during daytime. Recently, we observed that patients with untreated obstructive sleep apnea syndrome living at an altitude below 800 m revealed a major exacerbation of sleep apnea, pronounced hypoxemia, and impaired driving simulator performance during a stay in the mountains at altitudes of 1,860 m and 2,590 m. 13,14 If similarly striking effects would occur even in healthy individuals without preexisting breathing disorder, this would have major implications for a large number of travelers to moderate altitude as well as for flight passengers and air crew 15,16 in terms of impairment of subjective well-being, and performance during professional activities and sports. Therefore, the purpose of the current study was to perform a randomized trial evaluating the hypothesis that acute exposure to hypobaric hypoxia at moderate altitude during 4 days is associated with periodic breathing, sleep disturbances, and impaired psychomotor and cognitive function during daytime.…”