Cognition at altitude: impairment in executive and memory processes under hypoxic conditions.

BACKGROUND The negative effect of hypoxia on cognitive function has been well described. However, less has been published regarding cognitive dysfunction resulting from hypoxia produced by exposure to different altitudes. METHODS We measured short-term and working memory capacity (Digit Span tasks), cognitive flexibility and selective attention (Word-Color Stroop Task), and executive functioning (Trailmaking A and B tests) at baseline and simulated altitudes equal to 17,500 ft (5334 m) and 25,000 ft (7620 m) in order to obtain more information about the role of altitude exposure on cognitive tasks important for optimal functioning in the aviation environment. RESULTS Behavioral observations indicated that hypoxia was induced at different simulated altitudes. Marked declines in cognitive performance were also observed for all tests at 25,000 ft, with scores indicating greater impairment in this condition relative to others. Subjects also showed greater impairment when scores obtained in the 17,500-ft condition were compared to baseline, although the effects were not as clearly defined relative to the 25,000 vs. baseline contrasts. DISCUSSION The results of this study suggest that electronic versions of these tests may be useful in screening for acute symptoms of hypoxia and could provide insight into how discrete cognitive processes become impaired with oxygen deprivation at various altitudes. Given that these tests also assess neuropsychological functioning, our results allow for inferences to be made about the effects of hypoxia on human brain functioning.