Brain tumor risk decreased in allergy patients

Last Updated: 2007-11-07 14:12:02 -0400 (Reuters Health)

By Will Boggs, MD

NEW YORK (Reuters Health) - Patients with allergic conditions have a decreased risk of glioma, according to a report in the American Journal of Epidemiology. Gliomas are tumors of the central nervous system that are difficult to treat and are usually rapidly fatal.

"I am not sure that our findings have any clinical implications at the moment, but this should be further investigated by immunologists" to better understand how the immune system is involved in tumor formation, Dr. Annette Wigertz from the Karolinska Institute, Stockholm, told Reuters Health.

Wigertz and colleagues analyzed the association between a history of allergic conditions and the risk of glioma and meningioma for 100 patients in five European countries. Meningiomas are tumors of the tissue surrounding the brain (the meninges), which can be benign or malignant; the prognosis is variable.

A past diagnosis of asthma, hay fever, eczema, or other allergy was associated with a 30-percent reduction in the risk of glioma, the authors report, and the risk did not vary with the age at onset of the allergic condition.

There was no significant association between allergic conditions and the risk of meningioma, except for a decreased risk associated with eczema.

The reduction in the risk of glioma was greater in subjects with three or more allergic conditions (48 percent reduction) than in those with only one condition (24 percent reduction).

Patients who used eye drops or nasal spray for hay fever, compared with those who did not, had a significantly reduced risk of glioma, the investigators found, but the risk glioma was not significantly reduced by the use of oral antihistamines or desensitization therapy.

These findings may advance the understanding of how allergic conditions might reduce the risk of tumors, the researchers conclude, but the influence of bias, variables not taken into account, and other factors must be considered, which may lead to alternative explanations.

Further study of the related immunology is needed to uncover the reason for the inverse association between allergic conditions and glioma risk, Wigertz added. An opportunity for long-term follow-up of a large group of patients is also needed.

SOURCE: American Journal of Epidemiology, October 15, 2007.