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ORIGINAL ARTICLE
Year : 2016  |  Volume : 12  |  Issue : 8  |  Page : 301-303

Does smoking increase the risk of developing glioma? A meta-analysis based on case–control studies


Department of Neurology, Henan University Huaihe Hospital, Kaifeng, Henan, P.R. China

Date of Web Publication22-Feb-2017

Correspondence Address:
Xiaqing Guo
Department of Neurology, Henan University Huaihe Hospital, Kaifeng, Henan 475000
P.R. China
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/0973-1482.200758

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 > Abstract 

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

How to cite this URL:
Guo X, Wang Y. Does smoking increase the risk of developing glioma? A meta-analysis based on case–control studies. J Can Res Ther [serial online] 2016 [cited 2017 Aug 19];12:301-3. Available from: http://www.cancerjournal.net/text.asp?2016/12/8/301/200758

Xiaqing Guo and Yabo Wang contributed equally to this work.



 > Introduction Top


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.[1] Epidemiological data show that there are some differences in the incidence rate of cerebral gliomas in different regions.[2] However, in general, it accounts for about 50% of primary tumors of the central nervous system, and there is an upward trend.[3],[4] 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.[1] 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 Top


Publication searching

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.

Data extraction

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.

Statistical analysis

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 Top


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];[5],[6],[7],[8],[9],[10],[11] the general characteristics of the 7 case–control studies are shown in [Table 1].
Figure 1: The paper inclusion flowchart

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Table 1: The general information of the included seven papers

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Heterogeneity analysis

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.

Meta-analysis

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].
Figure 2: The forest plot for evaluation of smoking and glioma risk

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Publication bias

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].
Figure 3: The funnel plot for evaluation of publication bias

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 > Discussion Top


As everybody knows, smoking is associated with many carcinomas such as lung cancer, breast cancer, and oral cancer.[12],[13] The relationship between lung cancer and smoking is the most obvious; epidemiological data show that 90% of lung cancer is caused by smoking.[14],[15] 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.[6],[7] 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

Nil.

Conflicts of interest

There are no conflicts of interest.

 
 > References Top

1.
Ohgaki H, Kleihues P. Epidemiology and etiology of gliomas. Acta Neuropathol 2005;109:93-108.  Back to cited text no. 1
    
2.
Ostrom QT, Bauchet L, Davis FG, Deltour I, Fisher JL, Langer CE, et al. The epidemiology of glioma in adults: A “state of the science” review. Neuro Oncol 2014;16:896-913.  Back to cited text no. 2
    
3.
Milano MT, Johnson MD, Sul J, Mohile NA, Korones DN, Okunieff P, et al. Primary spinal cord glioma: A Surveillance, Epidemiology, and End Results database study. J Neurooncol 2010;98:83-92.  Back to cited text no. 3
    
4.
Schwartzbaum JA, Fisher JL, Aldape KD, Wrensch M. Epidemiology and molecular pathology of glioma. Nat Clin Pract Neurol 2006;2:494-503.  Back to cited text no. 4
    
5.
Preston-Martin S, Mack W, Henderson BE. Risk factors for gliomas and meningiomas in males in Los Angeles County. Cancer Res 1989;49:6137-43.  Back to cited text no. 5
    
6.
Hurley SF, McNeil JJ, Donnan GA, Forbes A, Salzberg M, Giles GG. Tobacco smoking and alcohol consumption as risk factors for glioma: A case-control study in Melbourne, Australia. J Epidemiol Community Health 1996;50:442-6.  Back to cited text no. 6
    
7.
Ryan P, Lee MW, North B, McMichael AJ. Risk factors for tumors of the brain and meninges: Results from the Adelaide adult brain tumor study. Int J Cancer 1992;51:20-7.  Back to cited text no. 7
    
8.
Lee M, Wrensch M, Miike R. Dietary and tobacco risk factors for adult onset glioma in the San Francisco Bay Area (California, USA). Cancer Causes Control 1997;8:13-24.  Back to cited text no. 8
    
9.
Zheng T, Cantor KP, Zhang Y, Chiu BC, Lynch CF. Risk of brain glioma not associated with cigarette smoking or use of other tobacco products in Iowa. Cancer Epidemiol Biomarkers Prev 2001;10:413-4.  Back to cited text no. 9
    
10.
Hu J, Johnson KC, Mao Y, Guo L, Zhao X, Jia X, et al. Risk factors for glioma in adults: A case-control study in Northeast China. Cancer Detect Prev 1998;22:100-8.  Back to cited text no. 10
    
11.
Brownson RC, Reif JS, Chang JC, Davis JR. An analysis of occupational risks for brain cancer. Am J Public Health 1990;80:169-72.  Back to cited text no. 11
    
12.
Jahn O. Passive smoking, a risk factor for lung carcinoma? Wien Klin Wochenschr 1996;108:570-3.  Back to cited text no. 12
    
13.
Hasan S, Dutt SN, Kini U, Shariff S, Nalinesha KM, Prasad D. Laryngeal carcinoma ex-papilloma in a non-irradiated, non-smoking patient: A clinical record and review of the literature. J Laryngol Otol 1995;109:762-6.  Back to cited text no. 13
    
14.
Takezaki T. Risk and protective factors in lung cancer other than the smoking habit. Nihon Rinsho 2002;60 Suppl 5:42-5.  Back to cited text no. 14
    
15.
Nakayama T, Kusunoki Y, Suzuki T. Influence of smoking and family history on the risk of lung cancer. Nihon Rinsho 2002;60 Suppl 5:39-41.  Back to cited text no. 15
    


    Figures

  [Figure 1], [Figure 2], [Figure 3]
 
 
    Tables

  [Table 1]



 

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