Reproductive factors and the risk of brain tumors: A population‐based study in Sweden

Abstract

Possible associations between childbearing and the risk of brain cancer were explored in a case-control study ''nested'' within a large nationwide cohort defined by the Swedish Fertility Registry. Among women born between 1925-1975, 1,088 patients with meningiomas and 1,657 patients with gliomas were identified in the Swedish Cancer Registry. For every woman diagnosed with brain tumor, 5 age-matched controls were selected among those in the Fertility Registry. Relative risks were estimated 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 between ever-parous and nulliparous women for gliomas, but not meningiomas, is difficult to explain biologically. A possible explanation is that pregnancy-induced alterations in androgen levels reduce the risk of glioma in parous women. Alternatively, childlessness may represent a marker of an occult glioma, negatively affecting fecundity. Overall, our 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. Int.

Reproductive factors and hormone use and risk of adult gliomas

“…These findings differ from a population-based study restricted to rural women in the upper Midwestern States (N=341 cases) which reported an elevated odds ratio (OR = 1.22 95% CI: 0.77–1.96) with ever giving birth and gliomas 15. Our results of no association with increasing number of children agree with most, but not all,12,19 previous studies.…”

“…Four of six studies reported parous women were at reduced risk of gliomas compared with nulliparous women. In the largest population based case control study to date (N=1657 glioma cases), Lambe et al reported a 24% reduced risk in ever parous Swedish women compared to nulliparous women (OR = 0.76 95% CI: 0.66–0.87) 12. A more recent but smaller hospital based case control study found similar, but non-significant, results (OR = 0.85 95% CI: 0.54 – 1.35),19 whereas odds ratio for parity were near the null in our study.…”

“…However, epidemiologic studies using reproductive and menstrual history as surrogates of hormone exposure have been generally inconclusive due, in part, to small sample sizes, different histology groupings among glioma classification systems, or the combining of heterogeneous histologic subtypes 12–22. We used data from the largest population-based case control study of adult brain tumors to date, the San Francisco Bay Area Adult Glioma Study, to estimate the effects of reproductive factors and hormone use on gliomas among women.…”

Sex steroid hormone exposures and risk for meningioma

“…20,29,32,33 In these studies the researchers found no significant relationship between meningioma risk and number of pregnancies. Although three of these studies comprised relatively few cases, the fourth, which was conducted within the Swedish Fertility Registry, was composed of more than 1000 cases with five age-matched controls.…”

Socioeconomic position and the risk of brain tumour: a Swedish national population-based cohort study

“…This could potentially explain the higher incidence in women with higher education. Hormonal and reproductive differences between the two sexes could also potentially explain the difference in incidence of meningioma and glioma between men and women 18 20 21…”