Nervous System

Although brain and other nervous system tumors are relatively rare, constituting up to 4% of incident primary cancer diagnoses, they are often associated with high morbidity and mortality. Several etiologic factors have been examined in relation to nervous system tumors, with the majority of studies focusing on central nervous system tumors. Despite decades of research, the only established risk factors for brain tumors are family history and moderate to high levels of ionizing radiation exposure. Differences in study designs, case ascertainment, control selection, and accuracy of exposure assessment are challenges associated with studying risk factors for nervous system tumors, and may partly explain why the majority of risk for these tumors remains unexplained. There is now substantial evidence that gliomas are inversely associated with allergies and atopy and positively associated with taller height.