Abstract
Background and ObjectivePrevious investigations of glioma risk in women have focused on oral contraceptive (OC), hormone replacement therapy (HRT), and reproductive factors. However, the results of published studies were inconclusive and inconsistent. Thus, a meta-analysis based on published case-control studies was performed to assess the role of exogenous and endogenous hormones factors in glioma risk.MethodsThe PubMed and EMBASE databases were searched without any restrictions on language or publication year. Reference lists from retrieved articles were also reviewed. We included case-control studies reporting relative risks (RRs) with corresponding 95% confidence intervals (CIs) (or data to calculate them) between oral contraceptive (OC) and hormone replacement therapy (HRT) use, reproductive factors and glioma. Random-effects models were used to calculate the summary risk estimates.ResultsFinally, 11 eligible studies with 4860 cases and 14,740 controls were identified. A lower risk of glioma was observed among women who were ever users of exogenous hormones (OC RR = 0.707, 95% CI = 0.604–0.828; HRT: RR = 0.683, 95% CI = 0.577–0.808) compared with never users. An increased glioma risk was associated with older age at menarche (RR = 1.401, 95% CI = 1.052–1.865). No association was observed for menopause status, parous status, age at menopause, or age at first birth and glioma risk.ConclusionThe results of our study support the hypothesis female sex hormones play a role in the development of glioma in women. Additional studies are warranted to validate the conclusion from this meta-analysis and clarity the underlying mechanisms.
Highlights
Glioma is the most common type of central nervous system tumor, which accounts for more than 70% of cases [1]
To determine to what extent hormonal and reproductive factors influence the risk of glioma in women, a number of studies have assessed the relationship between glioma and female-specific risk factors
Inclusion Criteria Studies were considered eligible if the studies met the following inclusion criteria: (1) a case-control study; (2) tested the association between oral contraceptive (OC), hormone replacement therapy (HRT), reproductive factors and glioma risk; (3) provided estimates of relative risk with corresponding 95% confidence intervals (CIs); (4) in case of multiple reports of the same trial, we selected the most recent publication with the largest number of subjects
Summary
Glioma is the most common type of central nervous system tumor, which accounts for more than 70% of cases [1]. The incidence of glioma is about 1.5 or 2 fold higher in men than in women, but the sex difference emerges in early adolescence, reaches a maximum around the age at menopause and decreases thereafter [3,4,5]. Both animal and biological experiments reinforced the epidemiological data. A meta-analysis based on published case-control studies was performed to assess the role of exogenous and endogenous hormones factors in glioma risk
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