The association between allergy and risk of brain tumors: Evidence from 40 observational studies

The potential association between the medical history of allergic conditions and brain tumors have been investigated. However, the agreement has not been reached. The aim of this meta-analysis was to explore the possible association between allergic disease and brain tumor risk.

A comprehensive search was conducted and eligible studies were identified. Random-effects model was applied to meta-analyze the data.

In accordance with the retrieval strategy, 40 articles with 31 case-control studies and 9 cohort studies were enrolled in the present meta-analysis. The results suggested that history of allergy was associated with a decreased risk of brain tumor (OR 0.78, 95% CI 0.71-0.86). Compared to individuals with 1 allergic condition (OR 0.78, 95% CI 0.71-0.85), those with at least 2 allergic conditions (OR 0.65, 95% CI 0.58-0.73) may have a potentially lower brain tumor risk. Moreover, decreased brain tumor risk was found in both adults (OR 0.75, 95% CI 0.69-0.81) and children/adolescents (OR 0.78, 95% CI 0.62-0.97). Allergy history is associated with a decreased risk of glioma (OR 0.71. 95% CI 0.61-0.81). Besides, glioma risk is negatively associated with asthma (OR 0.82, 95% CI 0.74-0.91) and eczema (OR 0.84, 95% CI 0.72-0.98). There is a tendency that allergy is associated with decreased risk of meningioma (OR 0.89, 95% CI 0.74-1.07).

Allergy should be considered as a protective factor for brain tumors, especially glioma. Further prospective cohort studies are needed to provide a higher level of evidence.