OBJECTIVE: Although causal relationships between smoking and cancer risk have 
been established for many sites, most studies of brain cancer have not supported 
an association. However, two recent cohort studies showed increased risks of 
glioma among smokers. We quantified the association between smoking and glioma 
through a meta-analysis of the literature.
METHODS: Of 20 eligible studies, 17 (6 cohort and 11 case–control) were included 
in an analysis of ever versus never smoking. Multivariate-adjusted risk 
estimates in the papers were pooled to calculate cumulative risk.
RESULTS: The cumulative estimated risk associated with ever smoking was 1.06 
(95% CI: 0.97–1.15), for all, 1.10 (95% CI: 1.01–1.20) for cohort, and 1.00 (95% 
CI: 0.88–1.15) for case–control studies. A significantly increased risk 
associated with past smoking was noted for cohort studies, OR = 1.16 (p = 
0.007), while an increased risk of borderline significance was seen for all 
studies, OR = 1.10 (p = 0.08). In general, dose–response analysis did not 
support an association and was limited because very few studies included these 
variables and could be pooled.
CONCLUSION: Overall, results of pooling of all studies suggested that smoking is 
not associated with risk of glioma. However, the small but significant increased 
risk seen for cohort studies remains to be clarified.