Effect of acute hypoxia on cognition: a systematic review and meta-regression analysis

A systematic meta-regression analysis of the effects of acute hypoxia on the performance of central executive and non-executive tasks, and the effects of the moderating variables, arterial partial pressure of oxygen (PaO2) and hypobaric versus normobaric hypoxia, was undertaken. Studies were included if they were performed on healthy humans; within-subject design was used; data were reported giving the PaO₂ or that allowed the PaO₂ to be estimated (e.g. arterial oxygen saturation and/or altitude); and the duration of being in a hypoxic state prior to cognitive testing was ≤6 days. Twenty-two experiments met the criteria for inclusion and demonstrated a moderate, negative mean effect size (g = −0.49, 95% CI −0.64 to −0.34, p < 0.001). There were no significant differences between central executive and non-executive, perception/attention and short-term memory, tasks. Low (35–60 mmHg) PaO₂ was the key predictor of cognitive performance (R² = 0.45, p < 0.001) and this was independent of whether the exposure was in hypobaric hypoxic or normobaric hypoxic conditions.