Effects of Acclimatization on Cognitive Function at High Altitude

Abstract

Acute high‐altitude exposure can lead to impaired neurocognitive function. However, it remains unclear if the duration of exposure impacts the degree of impairment or if acclimatization improves performance over time. We hypothesized that measures of sustained attention and reaction time would be impaired by acute high‐altitude exposure and would improve over three days of acclimatization. 14 participants (n=9 men; n=5 women) were included in the study. Participants completed a 30 minute cognitive function test battery (Cognition by Joggle Research) at sea level and each morning over three days at 3800 m elevation. Half of the participant group completed baseline sea‐level cognitive function testing before ascent to high altitude and half completed baseline tests at least 2 days after returning to sea level. The cognitive test battery evaluated sensory motor speed, visual learning, working memory and spatial working memory, abstraction, spatial orientation, complex scanning and visual tracking, risk decision making, and vigilant attention. Mean reaction time on the Psychomotor Vigilance Task (PVT) was higher at high‐altitude compared to sea level (SL: 199 ± 27 ms; Day 1 Alt: 224 ± 33 ms; p=0.005) and did not improve over three days of acclimatization. However, mean reaction time on the Line Orientation Task (LOT) was lower at high‐altitude compared to sea level (SL: 6076 ± 1831 ms; Day 1 Alt: 5173 ± 988 ms; p=0.02) and remained lower throughout acclimatization. The number of correct responses on the LOT did not change significantly upon ascent. Reaction times on the Digit Symbol Substitution Task (DSST) decreased (R=‐0.33, p=0.04) and the number of correct responses increased (R=0.32, p=0.04) throughout acclimatization. Mean reaction time on the Balloon Analog Risk Task (BART) decreased throughout acclimatization (R=‐0.35, p=0.02). These data suggest that while some cognitive domains including complex scanning and visual tracking (DSST) improve with acclimatization, behavioral alertness and sustained attention (PVT) remain impaired. Furthermore, spatial orientation measured by the LOT was improved at high altitude, consistent with studies showing no change, or improvements in visuospatial perception, under mild stress. Further work is required to determine the mechanisms underlying the effects of acclimatization on cognitive function, the domains in which improvement occurs, the time course of these changes, and whether interventions can impact these processes.Support or Funding InformationThis work was funded by the University of California, Riverside, School of Medicine.