Atopy and risk of brain tumors: A meta-analysis

Background: Glioma is a rapidly progressive disease, and little is known about its etiology. Atopic diseases are on the rise in western populations, with increasing interest on their long-term health consequences. An inverse association between atopy and the risk of glioma has been observed. We carried out a meta-analysis of studies examining the association between atopic disease and risk of glioma and meningioma. Methods: In an electronic literature search of the MEDLINE, ISI Web of Science, and EMBASE databases from 1979 through February 2007, we identified case-control and cohort studies quantifying associations between a history of asthma, eczema, or hay fever or allergy and a medically confirmed diagnosis of glioma or meningioma. We performed meta-analysis by pooling studies according to the inverse of their variances. We evaluated publication bias using funnel plot and sensitivity analyses. Results: A total of eight observational studies were included, with a total of 3450 patients diagnosed with glioma and 1070 patients with meningioma. A history of atopic disease was inversely related to risk of glioma. The pooled relative risks (RRs) of glioma comparing those with a history of an atopic condition with those with no history of that condition were 0.61 (95% confidence interval [CI] = 0.55 to 0.67) for allergy, 0.68 (95% CI = 0.58 to 0.80) for asthma, and 0.69 (95% CI = 0.58 to 0.82) for eczema. Proxy reporting was unlikely to explain the association because the pooled relative risk estimate from studies without proxy reporting remained inverse and statistically significant (RR = 0.66, 95% CI = 0.58 to 0.75). Publication bias was also an unlikely explanation for the inverse association because the association persisted in a sensitivity analysis and the funnel plot was symmetric. No overall statistically significant association was noted for atopy and meningioma, although the information on this disease was limited and heterogeneous. Conclusions: We observed a strong inverse relationship between atopic disease and glioma that is unlikely to be explained by methodologic bias alone.