Author(s): BOULARES, A., PICHON, A., FAUCHER, C., THEUROT, D., GIMENES, M., DUPUY, O., Institution: POITIERS UNIVERSITY , Country: FRANCE, Abstract-ID: 1494

INTRODUCTION:
Approximately 81.6 million individuals reside permanently at altitudes above 2,500 meters, with many more intermittently exposed to high-altitude environments through travel, work, or recreation. Hypoxia, a reduction in available oxygen, can adversely affect human physiology and cognitive performance. While younger adults often exhibit resilience to moderate hypoxia[1], the extent to which middle-aged adults experience cognitive changes remains less established. Age-related declines in neurovascular coupling and cerebral autoregulation may increase susceptibility to hypoxia-induced impairments, underscoring the importance of focused research in middle-aged adults.
METHODS:
Sixteen healthy participants (aged 45–65 years) were recruited to investigate the impact of acute normobaric hypoxia on cognitive performance and cerebral oxygenation. Each participant attended four separate sessions in a hypoxia chamber, simulating altitudes of 0 m (normoxia, FiO2≈20.9%), 1,500 m (low altitude, FiO2≈17.3%), 3,000 m (moderate altitude, FiO2≈14.5%), and 4,500 m (high altitude, FiO2≈12%). At each session, participants completed a cognitive test battery comprising the Stroop test, N-back task, Corsi block-tapping test, and Operation Span Task. Cerebral oxygenation was assessed continuously using near-infrared spectroscopy, measuring tissue saturation index (TSI), total hemoglobin (tHb), deoxyhemoglobin (HHb), and oxyhemoglobin (O2Hb). Changes in these parameters (ΔTSI%, ΔtHb, ΔHHb, and ΔO2Hb) were determined by subtracting normoxic resting values from those obtained during each hypoxia level. Perceived exertion was evaluated after each cognitive task using the DP15 rating scale.
RESULTS:
Exposure to graded hypoxia significantly impaired cognitive performance in middle-aged adults, particularly at moderate to high altitudes (3,000–4,500 m). Compared with normoxia, participants exhibited slower reaction times and decreased accuracy on the Stroop test (p < 0.05), reduced accuracy on the N-back task (p < 0.05), as well as on the Corsi block-tapping test (p < 0.05). These deficits were more pronounced under high-altitude conditions (4,500 m). Correlation analyses indicated a strong positive relationship between reduced oxygen availability (SpO2) and heightened perceived exertion (p < 0.05), suggesting that lower oxygen levels may directly contribute to cognitive performance decrements.
CONCLUSION:
Acute normobaric hypoxia at simulated moderate to high altitudes significantly affects cognitive function in middle-aged adults, underlining a potential vulnerability in this demographic. These findings emphasize the importance of monitoring and mitigating hypoxia-related risks for individuals exposed to lower oxygen environments and warrant further research into interventions that could preserve cognitive performance at altitude.