Cognitive Assessment Following Sleep Apnea Treatments at High Altitude
Authors: Djokic Matea A. , Heinrich Erica C. , Gilbertson Dillon , DeYoung Pamela , Bosompra Naa‐Oye , Orr Jeremy , Powell Frank L. , Malhotra Atul , Simonson Tatum S. 
Published: November 2023

Poor sleep quality is common at high altitude and likely influences memory consolidation and daytime cognitive function. However, the contribution of poor sleep quality versus hypoxemia to cognitive impairment is unknown. We hypothesized that supplemental O2 and adaptive servo‐ventilation (ASV), which reduces apneic events without supplemental O2, would improve sleep quality and/or specific aspects of cognitive performance at high altitude. Nineteen subjects (n = 13 males; n = 6 females) were studied at the University of California White Mountain Research Center, Barcroft Field Station (3800m). Subjects slept with ASV, supplemental oxygen (SpO2 > 95%), or no‐treatment (NT) randomized across three consecutive nights. Sleep quality was evaluated with polysomnography each night. Each morning, after treatment, subjects were given a battery of cognitive tests including the Psychomotor Vigilance Test (PVT), Attentional Network Test (ANT), Emotion Recognition Test (ERT), Balloon Analog Risk Task (BART), Trail Making Test A and B (TMT A, TMT B), Digit Span Test, Corsi Block Tapping Test, Verbal Paired Associates (VPA), Pittsburgh Sleep Quality Index (PSQI), Brunel Mood Scale, and Stanford Sleep Quality Scale. Data from 10 subjects analyzed, thus far, indicate no effect of treatment on the Apnea‐Hypopnea Index (AHI) (p=0.18) or the amount of time spent in stage 3 sleep (p=0.71), although there was a non‐significant trend for both supplemental oxygen and ASV to decrease average AHI. As expected, supplemental O2 increased blood oxygen saturation (SpO2) overnight (NT: 77.8±4.7, ASV: 80.1±4.2, O2: 95.3±4.1, p=0.06). ASV decreased sleep efficiency (NT: 0.83±0.12, ASV: 0.70±0.15, O2: 0.83±0.14, p=0.06) but did not increase sleep latency (p=0.93). This may indicate that participants require additional acclimation time with the ASV device prior to study. Lake Louise scores for acute mountain sickness (AMS) were highest following nights with no treatment (NT: 3.10±2.26, ASV: 1.80±0.97, O2: 1.22±1.20, p=0.05). Neither treatment resulted in consistently improved cognitive performance on the following morning. Apparent learning effects were observed for several cognitive tests. Time to complete the TMT B (R2=0.20; p<0.01) decreased over three days of administration. The PVT aggregate score increased over time (R2=0.18; p<0.02). A non‐significant trend for the correct number of responses on the ERT (R2=0.13; p>0.06) was observed. Finally, the BART indicated that individuals took fewer risks over time (R2=0.49; p<0.001). We conclude that the hypoxemia experienced at high altitude, during the testing period, may play a larger role in reducing cognitive performance than poor sleep quality. However, further analysis is required to determine the effectiveness of supplemental O2 and ASV on sleep quality at high altitude.

Support or Funding Information

UC San Diego Frontiers of Innovation Support for Center Development Grant and UC San Diego Undergraduate Research Scholarship ‐ Ledell Family Endowed Scholarship for Research and Engineering