Association between smoking and the risk of acute mountain sickness: a meta-analysis of observational studies

Abstract

BackgroundPeople rapidly ascending to high altitudes (>2500 m) may suffer from acute mountain sickness (AMS). The association between smoking and AMS risk remains unclear. Therefore, we performed a meta-analysis to evaluate the association between smoking and AMS risk.MethodsThe association between smoking and AMS risk was determined according to predefined criteria established by our team. Meta-analysis was conducted according to the PRISMA guidelines. We included all relevant studies listed in the PubMed and Embase databases as of September 2015 in this meta-analysis and performed systemic searches using the terms “smoking”, “acute mountain sickness” and “risk factor”. The included studies were required to provide clear explanations regarding their definitions of smoking, the final altitudes reached by their participants and the diagnostic criteria used to diagnose AMS. Odds ratios (ORs) were used to evaluate the association between smoking and AMS risk across the studies, and the Q statistic was used to test OR heterogeneity, which was considered significant when P < 0.05. We also computed 95% confidence intervals (CIs). Data extracted from the articles were analyzed with Review Manager 5.3 (Cochrane Collaboration, Oxford, UK).ResultsWe used seven case-control studies including 694 smoking patients and 1986 non-smoking controls to analyze the association between smoking and AMS risk. We observed a significant association between AMS and smoking (OR = 0.71, 95% CI 0.52–0.96, P = 0.03).ConclusionsWe determined that smoking may protect against AMS development. However, we do not advise smoking to prevent AMS. More studies are necessary to confirm the role of smoking in AMS risk.

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

“…Different selection criteria may lead to different results; we used strict inclusion criteria, high-quality studies, and control for confounding variables and heterogeneity by different methodological tools. Our meta-analysis results contrast with one meta-analysis [ 34 ] but accord with the other one [ 33 ]. Meta-analysis of 11 observational studies suggested an AMS incidence rate of 25.02%, being lower if the traveller climbed below 3500 MASL than if the traveller climbed higher than 3500 MASL.…”

“…Previous studies were systemically reviewed to explore the association between smoking and the risk of AMS because of the importance of this possible association in clinical practice and public health. To our knowledge, prior to our study, two meta-analyses explored the association between smoking and AMS [ 33 , 34 ] with different results. Vinnikov et al, 2016, found that smoking was not significantly associated with AMS (OR 0.88, 95% CI, 0.74 to 1.05) whereas Xu et al [ 34 ] found that smoking may protect against AMS development (OR 0.71, 95% CI, 0.52 to 0.96).…”

“…To our knowledge, prior to our study, two meta-analyses explored the association between smoking and AMS [ 33 , 34 ] with different results. Vinnikov et al, 2016, found that smoking was not significantly associated with AMS (OR 0.88, 95% CI, 0.74 to 1.05) whereas Xu et al [ 34 ] found that smoking may protect against AMS development (OR 0.71, 95% CI, 0.52 to 0.96). Different selection criteria may lead to different results; we used strict inclusion criteria, high-quality studies, and control for confounding variables and heterogeneity by different methodological tools.…”

Relationship of altitude mountain sickness and smoking: a Catalan traveller’s cohort study

“…In these studies, individuals were taken to very high altitudes (above 4000 masl), and the authors described smoking as a protective factor for AMS (RR=0.76 and 0.55, respectively), as found in a meta-analysis by Xu et al (pooled OR=0.71, 95% CI 0.52 to 0.96). 17 However, Li et al , 21 and Vinnikov et al 22 found smoking to be a risk factor (RR=1.11 and HR=1.9, respectively) when studying occupational cohorts or climbers commuting to very high altitudes (above 4000 masl), results that were in line with those shown in the meta-analysis performed by Vinnikov et al (pooled OR=0.88, 95% CI 0.74 to 1.05). 23 …”

“… 12–15 Around 30% of the world’s population declare being active smokers, yet there is a notable lack of consensus regarding the relationship between smoking and AMS risk. A recent meta-analysis performed by Vinnikov et al 16 showed that there was no significant association between smoking and AMS, while another performed by Xu et al 17 found an association between smoking and AMS, the former being a protective factor. The smoking status of travellers is not routinely explored, potentially resulting in an incomplete or misguided approach in the pretravel advice and treatment they receive.…”