AUTHOR=Pun Matiram , Guadagni Veronica , Bettauer Kaitlyn M. , Drogos Lauren L. , Aitken Julie , Hartmann Sara E. , Furian Michael , Muralt Lara , Lichtblau Mona , Bader Patrick R. , Rawling Jean M. , Protzner Andrea B. , Ulrich Silvia , Bloch Konrad E. , Giesbrecht Barry , Poulin Marc J. 

TITLE=Effects on Cognitive Functioning of Acute, Subacute and Repeated Exposures to High Altitude

JOURNAL=Frontiers in Physiology

VOLUME=Volume 9 - 2018

YEAR=2018

URL=https://www.frontiersin.org/journals/physiology/articles/10.3389/fphys.2018.01131

DOI=10.3389/fphys.2018.01131

ISSN=1664-042X

ABSTRACT=ABSTRACT
OBJECTIVE  
Neurocognitive functions are affected by high altitude, however the altitude effects of acclimatization and repeated exposures are unclear. We investigated the effects of acute, subacute and repeated exposure to 5050m on cognition among altitude-naïve participants compared to control subjects tested at low altitude.
METHODS 
Twenty-one altitude-naïve individuals (25.3±3.8 years, 13 females) were exposed to 5050m for one week (Cycle 1) and re-exposed after a week of rest at sea-level (Cycle 2). Baseline (BL, 520m), acute (Day 1, HA1) and acclimatization  (Day 6, HA6, 5050m) measurements were taken in both cycles. Seventeen control subjects (24.9±2.6 years, 12 females) were tested over a similar period in Calgary, Canada (1103m). The Reaction Time (RTI), Attention Switching Task (AST), Rapid Visual Processing (RVP) and One Touch Stockings of Cambridge (OTS) tasks were administered and outcomes were expressed in milliseconds/frequencies. Lake Louise Score (LLS) and blood oxygen saturation (SpO2) were recorded.
RESULTS  
In both cycles, no significant changes were found with acute exposure on the Attention Switching Task (AST) total score, mean latency and SD. Statistically significant changes were found upon acclimatization solely in the altitude group, with increased AST Mean Latency [HA1 (588±92) vs HA6 (526±91), p < 0.001] and Latency SD [HA1 (189±86) vs HA6 (135±65), p < 0.001]. No statistically significant differences were present in the control group. When entering Acute SpO2 (HA1-BL), Acclimatization SpO2 (HA6-BL) and LLS score as covariates for both cycle, the effects of acclimatization on AST outcomes disappeared indicating that the changes were partially explained by SpO2 and LLS. The changes in AST Mean Latency [∆BL (- 61.2±7.2) vs ∆HA6 (-28.0 ± 58), p = 0.005)] and the changes in Latency SD [∆BL (-28.4±41.2) vs ∆HA6 (-0.2235±34.8), p = 0.007)] across the two cycles decreased with acclimatization. However, the percent changes did not differ between cycles. These results indicate independent effects of altitude across repeated exposures. 
CONCLUSION  
Sustained attention is impaired at altitude and improves with acclimatization. The observed changes are associated, in part, with AMS score and SpO2. The gains in cognition with acclimatization during a first exposure are not carried over to repeated exposures.