REPRODUCTIVE FACTORS AND THE RISK OF BRAIN-TUMORS - A POPULATION-BASED STUDY IN SWEDEN

Possible associations between childbearing and the risk of brain cance r were explored in a case-control study ''nested'' within a large nati onwide cohort defined by the Swedish Fertility Registry. Among women b orn between 1925-1975, 1,088 patients with meningiomas and 1,657 patie nts with gliomas were identified in the Swedish Cancer Registry. For e very woman diagnosed with brain tumor, 5 age-matched controls were sel ected among those in the Fertility Registry. Relative risks were estim ated by odds ratios from conditional logistic regression. Ever-parous women were at a reduced risk of glioma compared to nulliparous women, while parity was unrelated to meningioma risk. Age at first birth was unrelated to both meningioma and glioma risk. The gradient in risk bet ween ever-parous and nulliparous women for gliomas, but not meningioma s, is difficult to explain biologically. A possible explanation is tha t pregnancy-induced alterations in androgen levels reduce the risk of glioma in parous women. Alternatively, childlessness may represent a m arker of an occult glioma, negatively affecting fecundity. Overall, ou r present results do not support the notion that hormonal changes, or other physiological changes induced by childbearing, play an important role in the development of brain tumors. (C) 1997 Wiley-Liss, Inc.