The more allergies people have, the lower their risk of developing low and high grade glioma or brain tumor, said US researchers in a study published this week.

You can read how researchers from the University of Illinois at Chicago came to these findings in the February issue of Cancer Epidemiology, Biomarkers & Prevention, a journal of the American Association for Cancer Research.

First author Dr Bridget McCarthy, a research associate professor of epidemiology at the University of Illinois at Chicago School of Public Health, told the press that previous studies have found a link between allergies and glioma risk, but in this study:

“… we confirmed that allergies are protective and found that the more allergies one has, the more protected he or she is.”

Glioma is a general name for a common type of primary brain tumor that starts in the supportive glial or neuroglial tissue of the brain.

For their research, McCarthy and colleagues used data from 419 patients with glioma and 612 cancer-free patients (the controls) from Duke University and North Shore University Health System.

The data came from responses to survey questions about medically diagnosed allergies and antihistamine use and the controls had no history of brain tumors, any other cancers, or neurodegenerative diseases.

McCarthy and colleagues were interested in analyzing links between the duration and timing of allergies, and antihistamine use and glioma risk, and how this might be affected by factors such as type and number of allergies, years since diagnosos, age at diagnosis of allergies, as well as type, duration and frequency of antihistamine use.

The participants completed the survey via web or telephone. The survey asked them questions about whether they were medically diagnosed with allergies or asthma at least two years ago, and if so, how old they were at diagnosis.

They also answered questions about the number of individual allergies within the following groups: “seasonal”, “pet”, “medication”, “food” and “other”, and any regular medication usage, including what brands, how often they took them and for how long.

When they analyzed the results the researchers found that:

  • Participants with high and low grade gliomas were statistically less likely to report any allergy than the controls (Odds Ratio OR 0.66; 95% Confidence Interval CI 0.49 – 0.87, and OR 0.44; 95% CI 0.25 – 0.76, respectively).

  • The number of types of allergy (seasonal, medication, pet, food, and other) was inversely linked with risk of developing glioma in a dose-response fashion, ie the more allergy types, the lower the risk (P value for trend less than 0.05, so not insignificant).

  • Age at diagnosis and years since diagnosis were not linked to glioma risk.

  • Oral antihistamine use, including diphenhydramine hydrochloride (a possible neurocarcinogen), did not appear to affect glioma risk separately from the effects of allergies.

The authors concluded that:

“All types of allergies appear to be protective with reduced risk for those with more types of allergies. Antihistamine use, other than in relationship with allergy status, may not influence glioma risk.”

McCarthy said these findings confirm there is a relationship between the immune system of allergy sufferers and risk of developing glioma.

She and her colleagues recommend that a comprehensive study now be done using standardized questions and biological markers, to assess effect of allergies and antihistamine use and discover what biological mechanisms might underpin any influence they have on brain tumor development.

“Assessment of Type of Allergy and Antihistamine Use in the Development of Glioma.”
Bridget J. McCarthy, Kristin Rankin, Dora Il’yasova, Serap Erdal, Nicholas Vick, Francis Ali-Osman, Darell D. Bigner, and Faith Davis.
Cancer Epidemiology, Biomarkers & Prevention, February 2011 20; 370
DOI: 10.1158/1055-9965.EPI-10-0948

Additional sources: American Association for Cancer Research (press release, 7 Feb 2011), American Brain Tumor Association.

Written by: Catharine Paddock, PhD