Effects of different exposures to normobaric hypoxia on cognitive performance in healthy young adults.

Normobaric hypoxia has become an innovative non-pharmacological therapy to treat cognitive dysfunction. Nevertheless, the acute effects of exposure to hypoxia on cognitive performance remain unclear. We aimed to determine the effects of different normobaric hypoxic exposures on cognitive function in healthy young adults. Nineteen participants (13 men and 6 women; 23.7 ± 3.9 years; 172.0 ± 8.4 cm; 69.1 ± 12.2 kg) completed a cross-over randomized control trial with the following doses of fraction of inspired oxygen (FiO₂): a) 21 %, b) 15 %, c) 13 % or d) 11 %. During experimental trials, the physiological response (blood oxygen saturation and heart rate) and the following cognitive abilities were evaluated: memory, sustained attention, anticipation, and reaction time. Sustained attention improved under hypoxia at 15 % FiO₂ (mean difference (MD) 0.024, 95 % confidence intervals (CI) 0.005 to 0.044 s; p = 0.018) compared to 11 % and 21 % FiO₂. During 11 % and 15 % FiO₂, participants showed improved anticipation ability compared to normoxia (MD -0.023, 95 % CI -0.042 to -0.003 s, p = 0.020, and MD -0.009, 95 % CI -0.016 to -0.001 s, p = 0.022, respectively). However, reaction time was impaired under 11 % compared to 21 % FiO₂ (MD 0.033, 95 % CI 0.008 to 0.059 s, p = 0.013). Finally, we did not find significant effects of hypoxia on memory (p > 0.05). Severe normobaric hypoxic exposure (11 % FiO₂) produces detrimental effects on reaction time, although anticipation seems to be improved, compared to normoxia. In addition, cognitive processes of attention and anticipation appear to improve with moderate hypoxic exposure (15 % FiO₂).