0303 The Effects of Latitude on Sleep at 4300m

Abstract

Abstract Introduction Worldwide, 140-million people live above 2400m and even more visit high altitudes (HA) annually. Exposure to HA is associated with hypoxia-related cognitive impairments and sleep disruptions. Additionally, both planetary axial tilt, solar gravity, and planetary spin distort the earth’s atmosphere pulling the equator’s atmosphere further from the earth’s surface when compared to the poles. These forces may have additional impacts on physiology at HA. There has yet to be a study to determine these effects of latitude on physiology at HA. Therefore, the aim of the current study was to determine if latitude exacerbates the effects of HA on sleep. Methods Similar testing protocols were utilized at 4,300m at Camp-14 on Denali at a latitude of ~63° and in the village of Dingboche on the route to Mount Everest at a latitude of ~28°. Exclusion criteria included 18-65 years, self-reported drug use, cigarette-smoking, sleep disorders, abnormal body mass index (BMI), falling asleep more than one hour or awakened more than an hour during the night. Wireless sleep recording devices recorded the sleep architecture of qualified participants. Twenty-two climbers (3 females) participated in the Denali study (age 34.0±9.7 mean±SD) and twenty-five climbers (6 females) participated in the Everest study (age 28.0±9.7 mean±SD). Participants were instructed to go to bed and wake up at their habitual bedtimes and wake times. Results Independent t-tests revealed a statistically significant decrease in total sleep (p<0.05) on Denali when compared to Mt. Everest. There were nonsignificant trends for a decrease in rapid eye movement (REM) and sleep onset latency on Denali. Other sleep stages appear relatively unaffected by latitude. Conclusion Our findings indicate that a decrease in total sleep time occurs at higher latitude with comparable altitude. Prior research has linked a decrease in total sleep time to decreased cognitive impairments and physiologic disruptions. Our findings suggest that latitude should be considered when venturing into HA environments, designing research protocols, analyzing results, and clinical applications or military operations. Support (If Any)