Active Ascent Does Not Alter Cognitive Performance Compared To Passive Ascent To 3600 m

Abstract

PURPOSE: Cognitive performance is known to decrease following acute exposure to high altitude (HA) but it is unknown whether active ascent affects that response. The purpose of this study was to examine changes in cognitive performance following active and passive ascent to 3600 m. METHODS: Forty-one healthy unacclimatized Soldiers (n = 41, mean ± SD; age = 26 ± 5 yr; body weight = 83.5 ± 11.6 kg; VO2max = 47.9 ± 5.5 ml · kg−1 · min−1) were tested at sea level (SL) in Ft. Leonard Wood, MO, flown to Taos Ski Valley, NM (2845 m) where they arrived around 1400 and then either hiked (n = 21; 5.0 km, 15.5% mean grade) or were driven (n = 20; 30-min drive) to a HA ski patrol facility located at 3600 m where they resided for the next 4 days. Energy expenditure during ascent was measured using an ankle accelerometer (Actical, Respironics, Inc.). Six cognitive modules (simple reaction time (SRT), match to sample (M2S), mathematical processing (MTH), procedural reaction time (PRO), simultaneous spatial processing (SPD) and simple reaction time 2 (SR2)) were administered using the Automated Neuropsychological Assessment Metrics in the morning (~0900) four times at SL, and following ~19 h at HA (HA2), and ~ 43 h at HA (HA3). All cognitive modules demonstrated no difference between the third (am) and fourth (pm) administrations at SL so the 3rd administration was used for the baseline record. RESULTS: The active group expended a greater (P < 0.05) amount of energy (745 ± 435 kcal) than the passive group (55 ± 10 kcal) during ascent. There were no differences in cognitive performance between groups so data were combined. The SRT decreased (P < 0.05) from SL (203 ± 28) to HA2 (192 ± 34) and increased (P < 0.05) from HA2 to HA3 (204 ± 29). PRO decreased (P < 0.05) from SL (97.5 ± 13.7) to HA2 (91.2 ± 14.9) and increased (P < 0.05) from HA2 to HA3 (96.1 ± 11.3). The SRT2 decreased (P < 0.05) from SL (195 ± 29) to HA2 (179 ± 46) and remained unchanged from HA2 to HA3 (188 ± 34). There were no changes in M2S, MTH, and SPD from SL to HA2 or HA3. CONCLUSION: Active compared to passive ascent did not impact cognitive performance at HA but reaction time whether simple, procedural, or repeated decreased on HA2. Both SRT and PRO recovered on HA3 but SR2, a measure of cognitive fatigue, did not recover. Authors’ views not official U.S. Army or DoD policy. Funding: USAMRDC