Prevalence and risk factors for AMS: A systematic review and meta-analysis

Clinical Snapshot

Key Findings

• P Value: Not reported in abstract

• Effect Size: Various risk ratios: extreme altitude RR=1.89, rapid ascent RR=1.60, heart rate increase RR=2.35

• Primary Outcome: AMS prevalence: 48.25% (95% CI: 42.58-53.96%)

• Nnt Or Sensitivity: Risk ratios ranging from 0.78 (protective effect of older age) to 2.35 (marked heart rate increase)

• Confidence Interval: 95% CI provided for prevalence and individual risk factors

Clinical Application

Risk stratification tools could be implemented in pre-travel consultations and occupational health assessments Relevant for Australian travellers to high-altitude destinations, military personnel, and adventure tourism. Could inform TGA altitude sickness medication guidelines and RACGP travel medicine recommendations Travellers, workers, and athletes exposed to high-altitude environments >2500m

Abstract

BACKGROUND: Acute Mountain Sickness (AMS) is a high-altitude-specific condition with variable prevalence and poorly defined risk factors. Despite growing global exposure to high-altitude environments, no systematic review has comprehensively synthesized AMS epidemiology. OBJECTIVES: To assess the prevalence of AMS and critically evaluate evidence on risk factors associated with increased susceptibility. DESIGN: A systematic review and meta-analysis following the Meta-analysis of Observational Studies in Epidemiology (MOOSE) guidelines. DATA SOURCES: PubMed, Cochrane Library, Web of Science, CINAHL Plus, China Knowledge Resource Integrated Database (CNKI), Wanfang Database, Chinese Biomedical Database (CBM), and Weipu Database (VIP) were comprehensively searched for observational studies investigating the prevalence and risk factors of AMS from January 1, 2004 to December 31, 2024. REVIEW METHODS: Original journal articles were included which met the inclusion criteria. The quality of the included studies was evaluated independently by two investigators. Meta-analysis was conducted using R software (v4.2.2), with estimates of AMS from pooled using a random-effects model. RESULTS: Fifty-eight studies (n = 2,705) were included. The pooled AMS prevalence was 48.25% (95% CI: 42.58-53.96%), with substantial heterogeneity (I² = 82.3%). Significant risk factors included extreme altitude (>5500 m; RR = 1.89), rapid ascent (<6 h; RR = 1.60), marked heart rate increase (>20 bpm; RR = 2.35), and oxygen saturation decline (>10%; RR = 2.02). Prior AMS history (RR = 1.36) and male sex (RR = 1.15) were also associated with higher risk, while older age (>50 years) was protective (RR = 0.78). CONCLUSION: AMS affects nearly half of high-altitude visitors. Altitude, ascent rate, cardiopulmonary response, and prior AMS history are key risk determinants. These findings support pre-exposure risk stratification, staged ascent protocols, and real-time physiological monitoring. PROSPERO CRD42024595365.

References

1. 1.Liu, X., Tan, L., Ren, Z., Bai, X., Yong, S., Gao, H., Ba, S., & Gongga, L. (2026). Prevalence and risk factors for AMS: A systematic review and meta-analysis. *PLoS One*. https://doi.org/10.1371/journal.pone.0345796