title: A pooled multisite analysis of the effects of female reproductive hormones on glioma risk.
abstract: OBJECTIVE
  The association between female reproductive factors and glioma risk is unclear, but most published studies have been limited by small sample size. We conducted a pooled multisite study of pre- and postmenopausal women, investigating the effect of female reproductive factors, including hormonal medications.
  
  
  METHODS
  Unconditional logistic regression was used to calculate odds ratios (ORs) and 95 % confidence intervals (95 % CIs) assessing the effects of female reproductive factors and female hormonal medications in glioma cases and unrelated controls.
  
  
  RESULTS
  Menarche over the age of 15 as compared to under 12 was associated with a statistically significant risk for glioma (OR 2.00, 95 % CI 1.47-2.71). Use of oral contraceptive pills (OCP) was inversely associated with risk of glioma (OR 0.61, 95 % CI 0.50-0.74), and there was an inverse trend with longer duration of OCP use (p for trend <0.0001). Use of hormone replacement therapy (HRT) was also inversely associated with risk of glioma (OR 0.55, 95 % CI 0.44-0.68), and there was an inverse trend with longer duration of use (p for trend <0.0001). Compared to those reporting neither OCP use nor HRT use, those who reported using both were less likely to have a diagnosis of glioma (OR 0.34, 95 % CI 0.24-0.48).
  
  
  CONCLUSIONS
  Female reproductive hormones may decrease the risk for glioma. The association appears to be strongest with greater length of use and use of both HRT and OCP.
authors.affiliation: Department of Medicine, New York Institute of Technology College of Osteopathic Medicine, Northern Boulevard, P.O. Box 8000, Old Westbury, NY, 11568-8000, USA, bkrishna@nyit.edu.
authors.forename: Bhuma
authors.initials: B
authors.lastname: Krishnamachari
authors.forename: Dora
authors.initials: D
authors.lastname: Il'yasova
authors.forename: Michael E
authors.initials: ME
authors.lastname: Scheurer
authors.forename: Melissa L
authors.initials: ML
authors.lastname: Bondy
authors.forename: Margaret
authors.initials: M
authors.lastname: Wrensch
authors.forename: Faith G
authors.initials: FG
authors.lastname: Davis
mesh_terms: D001932:Brain Neoplasms / Q000453:epidemiology* / Q000378:metabolism*; D016022:Case-Control Studies; D003278:Contraceptives, Oral, Hormonal / Q000008:administration & dosage*; D005260:Female; D005910:Glioma / Q000453:epidemiology* / Q000378:metabolism*; D012739:Gonadal Steroid Hormones / Q000378:metabolism*; D020249:Hormone Replacement Therapy / Q000706:statistics & numerical data*; D006801:Humans; D016015:Logistic Models; D008875:Middle Aged; D014481:United States / Q000453:epidemiology
chemical_list: D003278:Contraceptives, Oral, Hormonal; D012739:Gonadal Steroid Hormones