Assessment of type of allergy and antihistamine use in the development of glioma.

BACKGROUND Allergies have been associated with decreased risk of glioma; but, associations between duration and timing of allergies, and antihistamine use and glioma risk have been less consistent. The objective was to investigate this association by analyzing types, number, years since diagnosis, and age at diagnosis of allergies, and information on antihistamine usage, including type, duration, and frequency of exposure. METHODS Self-report data on medically diagnosed allergies and antihistamine use were obtained for 419 glioma cases and 612 hospital-based controls from Duke University and NorthShore University HealthSystem. RESULTS High- and low-grade glioma cases were statistically significantly less likely to report any allergy than controls (OR = 0.66, 95% CI: 0.49-0.87 and OR = 0.44, 95% CI: 0.25-0.76, respectively). The number of types of allergies (seasonal, medication, pet, food, and other) was inversely associated with glioma risk in a dose-response manner (P value for trend < 0.05). Age at diagnosis and years since diagnosis of allergies were not associated with glioma risk. Oral antihistamine use was statistically significantly inversely associated with glioma risk, but when stratified by allergy status, remained significant only for those with high-grade glioma and no medically diagnosed allergy. CONCLUSIONS 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. IMPACT A comprehensive study of allergies and antihistamine use using standardized questions and biological markers will be essential to further delineate the biological mechanism that may be involved in brain tumor development.