The Effects of Nocturnal Hypoxemia on Cognitive Performance in Andean Highlanders.

Background: Many Andean highlanders exposed to chronic hypoxemia are susceptible to excessive erythrocytosis (EE) and chronic mountain sickness (CMS). Nocturnal hypoxemia is more marked than diurnal hypoxemia and includes sustained and intermittent components. The potential for cognitive impairments related to nocturnal hypoxemia in this population has not been extensively studied, but improved understanding may provide opportunities for the prevention of long-term effects of EE and CMS. Methods: To examine this relationship, 48 participants residing permanently at 4,340 m completed an overnight sleep study and a battery of cognitive function tests that examined a broad range of cognitive domains. Results: Greater nocturnal hypoxemia was associated with longer reaction times on Balloon Analogue Risk Task (BART) (p < 0.01) and Emotion Recognition Test (ERT) (p < 0.01). Longer completion times of Trail Making Task were also associated with increased nocturnal hypoxemia (p = 0.03). Increased hematocrit was similarly associated with longer reaction times on the ERT (p = 0.01) and the BART (p = 0.01). Conclusion: Overall, our results showed that increased nocturnal hypoxemia and higher hematocrit were associated with impairments in cognitive performance in individuals residing permanently at high altitude.