Association Between Decreased Pulse Oximetry and Acute Mountain Sickness Upon Rapid Ascent to 4,086 m Among Young Chinese Men

Tang, Xu-gang, Xiu-chuan Li, Bao-mei Song, Shuang Li, Qiang Wang, and Yong-jian Yang. Association between decreased pulse oximetry and acute mountain sickness upon rapid ascent to 4,086 m among young Chinese men. High Alt Med Biol. 27:49–46, 2026. Background: Research on predicting acute mountain sickness (AMS) based on the decreased pulse oximeter saturation (SpO 2 ) during rapid train travel to high altitudes is limited and inconsistent. We aimed to assess whether lower SpO 2 levels are associated with AMS in a young Chinese male population following a rapid ascent to high altitude by train. Methods: The study involved 375 young Chinese men with a median age of 21. The participants spent 43 hours ascending from an altitude of 400 m to 4,086 m, including 41 hours by train and 2 hours by car. They were divided into AMS+ and AMS− groups based on the Lake Louise AMS score (LLS) after being exposed to 4,086 m for 24 hours. Participants’ SpO 2 and heart rate (HR) were measured. AMS was assessed using the LLS. Data were analyzed using Spearman’s correlation, logistic regression, and receiver operating characteristic (ROC) analysis. Results: At 4,086 m, the overall AMS prevalence was 31%. The HR was significantly higher in the AMS+ group compared to the AMS− group. Conversely, SpO 2 was lower in the AMS+ group. Correlation analysis showed that LLS was positively correlated with HR and negatively correlated with SpO 2 . Adjusted logistic regression identified lower SpO 2 (OR = 0.909, 95% CI: 0.867–0.953, p < 0.001) and HR (OR = 1.031, 95% CI: 1.010–1.052, p < 0.01) as independent risk factors for AMS. ROC analysis indicated that lower SpO 2 is a significant marker for diagnosing moderate to severe AMS. The optimal cut-off value for SpO 2 was 81.5%, with a sensitivity of 66.7%, a specificity of 75.7%, and an AUC of 0.724, with lower and upper confidence limits of 0.555 and 0.893, respectively. Conclusion: This study suggests that lower SpO 2 levels are associated with AMS in young Chinese men who rapidly ascend to 4,086 m, primarily by train.