Relationship between Smoking and Acute Mountain Sickness: A Meta-Analysis of Observational Studies

AIMS: Previous epidemiological investigations of the relationship between smoking and acute mountain sickness (AMS) risk yielded inconsistent findings. Therefore, a meta-analysis of observational studies was performed to determine whether smoking is related to the development of AMS. METHODS: Searches were performed on PubMed, Scopus, Embase, and Web of Science for relevant studies that were published before November 2016 reporting smoking prevalence and AMS. Two evaluators independently selected studies, extracted data, and assessed study quality. The pooled relative risks (RRs) and 95% confidence intervals (CIs) were obtained using random-effects models. Subgroup analyses were performed according to the type of participant, altitude, and study design. RESULTS: A total of 11 observational studies involving 7,106 participants, 2,408 of which had AMS, were eligible for inclusion in this meta-analysis. The summary RR for AMS comparing smokers to nonsmokers was 1.02 (95% CI: 0.83 to 1.26). Specific analyses for altitude, type of participant, and study design yielded similar results. There was significant heterogeneity for all studies (Q = 37.43; P < 0.001; I(2) = 73%, 95% CI: 51% to 85%). No publication bias was observed (Egger's test: P = 0.548, Begg's test: P = 0.418). CONCLUSIONS: The meta-analysis indicates that no difference was found in AMS risk with regard to smoking status.