Mood State Is Related To Acute Mountain Sickness At Both 3000m And 4050m Altitude

Abstract

PURPOSE: The purpose of this study was to further explicate the relationship between changes in mood states, assessed using the Automated Neuropsychological Assessment Metrics Mood Scale (ANAM-MS), and severity of acute mountain sickness (AMS) without the confounding factors of acetazolamide, climbing rate and environmental conditions. METHODS: Nineteen healthy lowlanders (16 men, 3 women; mean±SE; 22 ±1yr, 76.6 ±3.1 kg, 173.2 ±2.1cm, 46.0 ±1.2 ml · kg−1 · min−1) were randomly exposed to either 3000m (526mmHg) or 4050m (460mmHg) in a hypobaric chamber for 20h. Seven mood states (anger, anxiety, happiness, fatigue, depression, restlessness, and vigor) were assessed using the ANAM-MS; a series of 42 questions answered on a 0-6 Likert Scale. AMS severity was assessed using the AMC-Cerebral Factor Score (AMS-C) of the Environmental Symptoms Questionnaire. Both tests were administered on 8 occasions at sea level (SL), and after 2h and 20h at each altitude (HA2 and HA20). The SL baseline scores for ANAM-MS and AMS-C were calculated as the mean of the 7th (morning) and 8th (afternoon) assessments. RESULTS: There were no differences between altitude groups in mood at SL, HA2 or HA20 so data were combined. There was differences between altitude groups in AMS-C score so data was analyzed separately. No mood state changed significantly from SL to HA2. However, fatigue and restlessness increased (P<0.05) from SL (0.57 ±0.13; 0.07 ±0.03) to HA20 (1.41 ±0.32; 0.52 ±0.20), respectively. In addition, vigor decreased (P<0.05) from SL (1.97 ±0.30) to HA20 (0.88 ±0.21). Happiness, anxiety, depression and anger did not change over time. AMS-C was elevated (P<0.05) at 4050m (1.82 ±0.27) compared to 3000m (0.22 ±0.29) at HA20. Restlessness (r=0.66; P=0.037) and anxiety (r=0.65; P=0.044) correlated with AMS-C at HA20 in the 4050m group. Fatigue (r=0.77; P<0.016) and anger (r=0.95; P=0.0001) correlated with AMS-C at HA20 in the 3000m group. CONCLUSION: ANAM-MS ratings of fatigue, restlessness and decreased vigor emerge as low as 3000m due to hypobaric hypoxia alone. Mood disturbances were related to AMS severity; subjects with the highest ratings of fatigue and anger at 3000m, and restlessness and anxiety at 4050m possessed the highest AMS-C scores in their respective groups. Authors’ views not official U.S. Army or DoD policy. Funding: USAMRDC