Diabetes mellitus might be a protective factor of glioma

Aims: Several studies suggested that diabetes mellitus (DM) was associated with the risk of glioma. However, other studies did not confirm the result. Therefore, I conducted this meta-analysis. Materials and Methods: I retrieved the PubMed, Embase, and Web of Science database, by adopting keywords "glioma," and "diabetes," "DM." The strength of the associations between DM and the risk of glioma was measured by odds ratios (ORs) with 95% confidence intervals (95% CIs). Results: Ten relevant studies were identified in the final analysis. A statistically significant association between DM and glioma risk was fond (OR = 0.84; 95% CI, 0.73-0.97; P = 0.02). In the subgroup analysis of age group, young population with DM showed decreased glioma risk (OR = 0.83; 95% CI, 0.70-0.98; P = 0.02), whereas old population with DM did not show a significant association (OR = 0.87; 95% CI, 0.65-1.16; P = 0.34). In the subgroup analysis of gender, male patients with DM showed decreased glioma risk (OR = 0.82; 95% CI, 0.68-0.99; P = 0.04), whereas female population with DM did not show a significant association (OR = 0.93; 95% CI, 0.70-1.24; P = 0.63). Conclusions: This meta-analysis suggested that DM may be associated with the reduced glioma risk.