Allergies appear to lower brain tumor risk

By Helen Albert, Senior MedWire Reporter

Testing positive for immunoglobulin E (IgE), a biomarker of allergy, reduces a person's risk for developing glioma, show study findings.

"It could be that in allergic people, higher levels of circulating antibodies may stimulate the immune system, and that could lower the risk of glioma," said lead study author Judith Schwartzbaum (The Ohio State University, Columbus, USA) in a press statement.

"Absence of allergy is the strongest risk factor identified so far for this brain tumor, and there is still more to understand about how this association works."

Schwartzbaum and team explain that some previous studies have suggested an inverse link between levels of IgE and glioma risk, but findings have overall been inconsistent.

To investigate further, the researchers analyzed blood samples from 594 blood donors who were subsequently diagnosed with glioma between 1974 and 2007 and from 1177 controls who were not. The controls were matched to the glioma patients based on date of blood collection, approximate age (maximum 2-year difference), and gender.

Overall, those who tested positive for total IgE (>100 kU/L) had a significant 25% decreased risk for glioma compared with those who tested negative (=100 kU/L).

This effect was present at 20 years prior to glioma diagnosis, with those testing negative for total IgE at this time point having a significant 54% increased risk for glioma than those testing positive.

"This is our most important finding," said Schwartzbaum. "The longer before glioma diagnosis that the effect of allergies is present, the less likely it is that the tumor is suppressing allergies. Seeing this association so long before tumor diagnosis suggests that antibodies or some aspect of allergy is reducing tumor risk."

In addition to the findings for total IgE, women who tested positive for allergen-specific IgE (>0.35 kU_A/L) had a significant 54% reduced risk for glioma compared with women who tested negative (=0.35 kU_A/L), although no significant association was seen in men.

"There is definitely a difference in the effect of allergen-specific IgE between men and women. And even results for total IgE suggest there still may be a difference between the sexes. The reason for this difference is unknown," Schwartzbaum commented.

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