|Year : 2016 | Volume
| Issue : 8 | Page : 301-303
Does smoking increase the risk of developing glioma? A meta-analysis based on case–control studies
Xiaqing Guo, Yabo Wang
Department of Neurology, Henan University Huaihe Hospital, Kaifeng, Henan, P.R. China
|Date of Web Publication||22-Feb-2017|
Department of Neurology, Henan University Huaihe Hospital, Kaifeng, Henan 475000
Source of Support: None, Conflict of Interest: None
Objective: The purpose of this study was to assess the relationship between smoking and glioma risk by meta-analysis.
Materials and Methods: We have searched the databases of MEDLINE, EMBASE, Ovid, and CNKI to find the suitable studies related to association between smoking and glioma risk. The pooled odds ratio (OR) and 95% confidence interval (CI) of smokers in glioma patients compared to normal controls were aggregated by statistic software Stata11.0. The publication bias was evaluated by Begg's funnel plot.
Results: Finally, seven case–control studies were included in this meta-analysis. The pooled results showed that smoking did not increase the risk of glioma (OR = 0.96, 95% CI = 0.86–1.07, P > 0.05).
Conclusion: No close association between smoking and glioma risk was found in this meta-analysis, which indicate that smoking may not contribute to the incidence of glioma.
Keywords: Glioma, meta-analysis, risk, smoking
|How to cite this article:|
Guo X, Wang Y. Does smoking increase the risk of developing glioma? A meta-analysis based on case–control studies. J Can Res Ther 2016;12:301-3
Xiaqing Guo and Yabo Wang contributed equally to this work.
| > Introduction|| |
Brain glioma is the most common tumor with relative poor prognosis in primary central nervous system, but its etiology and pathogenesis are still not very clear. Epidemiological data show that there are some differences in the incidence rate of cerebral gliomas in different regions. However, in general, it accounts for about 50% of primary tumors of the central nervous system, and there is an upward trend., In recent years, epidemiological studies have shown that there may be a certain relationship between the occurrence of brain glioma and family genetic susceptibility, eating habits, alcohol consumption, ionizing radiation, electromagnetic fields, mobile phones, and other factors. In addition, some studies have shown that smoking may be a risk factor for brain glioma, but there are some differences between the results of the study. Therefore, this study retrieved the published data on the relationship between smoking and brain glioma and made the meta-analysis to further explore whether smoking increases the risk of brain glioma by evidence-based medicine.
| > Materials and Methods|| |
We have searched the databases of MEDLINE, EMBASE, Ovid, and CNKI to find the suitable studies related to association between smoking and glioma risk. The searching items were “smoking,” “glioma,” “risk factors,” and “brain tumor.”
Inclusion and exclusion criteria
Inclusion criteria: (1) study type - case–control study; (2) patients - the patients were glioma with confirmed diagnosis; (3) results - number of smokers and nonsmokers can be extracted from the original studies. For exclusion criteria: (1) Review or case report studies; (2) Without confirmation diagnosis of glioma; (3) duplicated studies.
Two reviewers extracted the original data independently. The extracted data included article title, author, year of publication, control type, race, number of cases and control, and number of smokers in case and control groups.
Data were calculated by Stata12.0 software (Stata Corporation, College Station, USA). The association between smoking and glioma risk was assessed by odds ratio (OR) and its 95% confidence interval (95% CI). The heterogeneity was assessed by Chi-square test, and publication bias was evaluated by funnel plot and linear regression test.
| > Results|| |
General information for the included seven case–control studies
After searching the databases, we found that 126 publications were potential suitable for our study. After reading the abstract and full text, 119 studies were excluded and finally 7 studies were included in our present meta-analysis [Figure 1];,,,,,, the general characteristics of the 7 case–control studies are shown in [Table 1].
We used the effect size of OR as the effect size to evaluate the heterogeneity. I2 was 48.0% which indicated no significant heterogeneity across the included seven studies. Then, the data were pooled by fixed effects model.
Without statistical heterogeneity, the data were pooled by fixed effects model. The combined results showed that smoking did not increase the risk of glioma (OR = 0.96, 95% CI = 0.86–1.07, P > 0.05) [Figure 2].
The publication bias was assessed by funnel plot and linear regression test. Funnel plot and linear regression test indicated no publication bias (t - 0.30, P > 0.05) [Figure 3].
| > Discussion|| |
As everybody knows, smoking is associated with many carcinomas such as lung cancer, breast cancer, and oral cancer., The relationship between lung cancer and smoking is the most obvious; epidemiological data show that 90% of lung cancer is caused by smoking., In the combustion process, tobacco can produce hundreds of carcinogens, and these harmful substances inhaled by the human being for a long period will significantly increase the risk of certain tumors. Recently, clinical case–control studies found that cigarette smoking may increase the risk of developing glioma., However, other studies found that there was no association between smoking and glioma risk. To further evaluate the association between cigarette smoking and glioma risk, we searched the open published studies related to smoking and glioma risk and pooled the data by meta-analysis method.
In this meta-analysis, we finally included seven case–control studies related to smoking and glioma risk. The pooled data showed that smoking did not increase the risk of glioma (OR = 0.96, 95% CI = 0.86–1.07, P > 0.05). This result indicated no close association between smoking and glioma risk, which indicate that smoking may not contribute to the incidence of glioma. However, number of cases and controls in each included original study was relative small and only seven case–control studies were included in this meta-analysis. Hence, the statistical power is limited. Therefore, whether cigarette smoking can increase the risk of developing glioma or not is not clear which needs to be demonstrated by large prospective cohort study.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2], [Figure 3]