Cognition and Neuropsychological Changes at Altitude—A Systematic Review of Literature

Abstract

High-altitude (HA) exposure affects cognitive functions, but studies have found inconsistent results. The aim of this systematic review was to evaluate the effects of HA exposure on cognitive functions in healthy subjects. A structural overview of the applied neuropsychological tests was provided with a classification of superordinate cognitive domains. A literature search was performed using PubMed up to October 2021 according to PRISMA guidelines. Eligibility criteria included a healthy human cohort exposed to altitude in the field (at minimum 2440 m [8000 ft]) or in a hypoxic environment in a laboratory, and an assessment of cognitive domains. The literature search identified 52 studies (29 of these were field studies; altitude range: 2440 m–8848 m [8000–29,029 ft]). Researchers applied 112 different neuropsychological tests. Attentional capacity, concentration, and executive functions were the most frequently studied. In the laboratory, the ratio of altitude-induced impairments (64.7%) was twice as high compared to results showing no change or improved results (35.3%), but altitudes studied were similar in the chamber compared to field studies. In the field, the opposite results were found (66.4 % no change or improvements, 33.6% impairments). Since better acclimatization can be assumed in the field studies, the findings support the hypothesis that sufficient acclimatization has beneficial effects on cognitive functions at HA. However, it also becomes apparent that research in this area would benefit most if a consensus could be reached on a standardized framework of freely available neurocognitive tests.

Mechanism, prevention and treatment of cognitive impairment caused by high altitude exposure

“…From gross inspection, the impairment severity is influenced by the level of altitude gain and higher altitudes have more serious consequences ( Yan, 2014 ). Minimal impairments have been noted at moderate altitudes of 2000–3,000 m, noticeable psychomotor impairments have been seen at 3,000–4,000 m, above 5,000 m, spatial memory was significantly impaired, and impairments in encoding and short-term memory were particularly evident at extremely HAs over 6,000 m ( Virués-Ortega et al, 2004 ; Wilson et al, 2009 ; Zhang et al, 2011 ; Bliemsrieder et al, 2022 ). Furthermore, a study employing the Mood State Inventory, the Clyde Mood Scale, and the Multiple Affective Adjectives Checklist to assess the emotional and cognitive performance of subjects confirmed over 20 years ago that exposure to altitudes above 3,000 m adversely affects individuals’ emotional and cognitive performance.…”