Association between physiological responses after exercise at low altitude and acute mountain sickness upon ascent is se
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RESEARCH
Open Access
Association between physiological responses after exercise at low altitude and acute mountain sickness upon ascent is sex-dependent Yang Shen1,2†, Yuan-Qi Yang1,2†, Chuan Liu1,2, Jie Yang1,2, Ji-Hang Zhang1,2, Jun Jin1,2, Hu Tan1,2, Fang-Zheng-Yuan Yuan1,2, Jing-Bin Ke1,2, Chun-Yan He1,2, Lai-Ping Zhang1,2, Chen Zhang1,2, Jie Yu1,2 and Lan Huang1,2*
Abstract Background: Acute mountain sickness (AMS) is the mildest form of acute altitude illnesses, and consists of nonspecific symptoms when unacclimatized persons ascend to elevation of ≥2500 m. Risk factors of AMS include: the altitude, individual susceptibility, ascending rate and degree of pre-acclimatization. In the current study, we examined whether physiological response at low altitude could predict the development of AMS. Methods: A total of 111 healthy adult healthy volunteers participated in this trial; and 99 (67 men and 32 women) completed the entire study protocol. Subjects were asked to complete a 9-min exercise program using a mechanically braked bicycle ergometer at low altitude (500 m). Heart rate, blood pressure (BP) and pulse oxygen saturation (SpO2) were recorded prior to and during the last minute of exercise. The ascent from 500 m to 4100 m was completed in 2 days. AMS was defined as ≥3 points in a 4-item Lake Louise Score, with at least one point from headache wat 6–8 h after the ascent. Results: Among the 99 assessable subjects, 47 (23 men and 24 women) developed AMS at 4100 m. In comparison to the subjects without AMS, those who developed AMS had lower proportion of men (48.9% vs. 84.6%, P < 0.001), height (168.4 ± 5.9 vs. 171.3 ± 6.1 cm, P = 0.019), weight (62.0 ± 10.0 vs. 66.7 ± 8.6 kg, P = 0.014) and proportion of smokers (23.4% vs. 51.9%, P = 0.004). Multivariate regression analysis revealed the following independent risks for AMS: female sex (odds ratio (OR) =6.32, P < 0.001), SpO2 change upon exercise at low altitude (OR = 0.63, P = 0.002) and systolic BP change after the ascent (OR = 0.96, P = 0.029). Women had larger reduction in SpO2 after the ascent, higher AMS percentage and absolute AMS score. Larger reduction of SpO2 after exercise was associated with both AMS incidence (P = 0.001) and AMS score (P < 0.001) in men but not in women. Conclusions: Larger SpO2 reduction after exercise at low altitude was an independent risk for AMS upon ascent. Such an association was more robust in men than in women. (Continued on next page)
* Correspondence: [email protected] † Yang Shen and Yuan-Qi Yang contributed equally to this work. 1 Institute of Cardiovascular Diseases of PLA, the Second Affiliated Hospital, Army Medical University, Chongqing 400037, China 2 Department of Cardiology, the Second Affiliated Hospital, Army Medical University, Chongqing 400037, China © The Author(s). 2020 Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit
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