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

Table 3

Subgroup analyses of RRs for the association between AMS and smoking.

Group	Number of studies	Pooled RR (95% CI)	Heterogeneity
			Overall	11	1.02 (0.83, 1.26)	73.0%	<0.001
Study design
Cross-sectional studies and case-control study	8	1.20 (0.99, 1.47)	32.0%	0.169
Cohort studies	3	0.79 (0.54, 1.17)	89.0%	<0.001
Altitude
<3500 MASL	2	1.24 (0.78, 1.95)	25.0%	0.922
≥3500 MASL	9	1.00 (0.79, 1.26)	78.0%	<0.001
Quality assessment
NOS/aNOS = 5	7	1.17 (0.97, 1.41)	23.0%	0.253
NOS/aNOS = 6-7	4	0.92 (0.62, 1.36)	87.0%	<0.001
Type of participant
Mountaineer	7	1.17 (0.97, 1.41)	23.0%	0.253
Nonmountaineer	4	0.92 (0.62, 1.36)	87.0%	<0.001

AMS: acute mountain sickness; CI: confidence interval; MASL: meters above sea level; NOS: Newcastle-Ottawa Quality Assessment Scale; aNOS: adapted Newcastle-Ottawa Quality Assessment Scale; RR: relative risks. Relative risks were obtained using the DerSimonian and Laird random-effect model.