Reproductive factors and risk of glioma in women.
OBJECTIVE
Glioma is the most common primary malignant brain tumor in adults, responsible for 75% of adult primary malignant brain tumors, yet aside from its association with ionizing radiation, its etiology is poorly understood. Sex differences in brain tumor incidence suggest that hormonal factors may play a role in the etiology of these tumors, but few studies have examined this association in detail. The objective of this study was to explore the role of reproductive factors in the etiology of glioma in women.


METHODS
As part of a population-based case-control study, histologically confirmed primary glioma cases (n = 341 women) diagnosed between January 1, 1995 and January 31, 1997 were identified through clinics and hospitals in four Midwest U.S. states. Controls (n = 527 women) were randomly selected from lists of licensed drivers and Health Care Finance Administration enrollees. In-person interviews with subjects (81%) or their proxies (19%) collected reproductive history and other exposure information.


RESULTS
Glioma risk increased with older age at menarche (P for trend = 0.009) but only among postmenopausal women. Compared with women who never breast-fed, women who breast-fed >18 months over their lifetime were at increased risk of glioma (odds ratio, 1.8; 95% confidence interval, 1.1-2.9). Women who reported using hormones for symptoms of menopause had a decreased risk of glioma compared with women who never used such hormones (odds ratio, 0.7; 95% confidence interval, 0.5-1.1).


CONCLUSIONS
These results support the hypothesis that reproductive hormones play a role in the etiology of glioma among women.
National Institute for Occupational Safety and Health, 4676 Columbia Parkway, Cincinnati, OH 45226, USA.
Kui
K
Huang
Elizabeth A
EA
Whelan
Avima M
AM
Ruder
Elizabeth M
EM
Ward
James A
JA
Deddens
Karen E
KE
Davis-King
Tania
T
Carreón
Martha A
MA
Waters
Mary Ann
MA
Butler
Geoffrey M
GM
Calvert
Paul A
PA
Schulte
Zachary
Z
Zivkovich
Ellen F
EF
Heineman
Jack S
JS
Mandel
Roscoe F
RF
Morton
Douglas J
DJ
Reding
Kenneth D
KD
Rosenman
D000328:Adult; D000367:Age Factors; D017668:Age of Onset; D000368:Aged; D001932:Brain Neoplasms / Q000453:epidemiology* / Q000209:etiology* / Q000517:prevention & control; D001942:Breast Feeding; D016022:Case-Control Studies; D016021:Epidemiologic Studies; D015914:Estrogen Replacement Therapy; D005260:Female; D005910:Glioma / Q000453:epidemiology* / Q000209:etiology*; D006801:Humans; D008572:Menarche; D008875:Middle Aged; D017698:Postmenopause; D012307:Risk Factors