title: Hormonal contraceptive use and risk of glioma among younger women: a nationwide case-control study.
abstract: OBJECTIVE
  Oral contraceptive use influences the risk for certain cancers. However, few studies have examined any link with risk of central nervous system tumours. We investigated the association between hormonal contraceptive use and glioma risk among premenopausal women in a population-based setting.
  
  
  METHODS
  Using national administrative and health registries in Denmark to conduct a nationwide case-control study, we identified all women ages 15 to 49 years with a first time diagnosis of histologically verified glioma between 2000 and 2009. Each case was age-matched to eight population controls using risk set sampling. Based on prescription data, exposure until 2 years prior to the index date was categorized according to hormonal contraceptive type, i.e. combined oestrogen-progestagen or progestagen only, and duration of use (<1, 1 to <5, ≥5 years). We used conditional logistic regression to compute odds ratios (ORs) with 95% confidence intervals (CIs) for glioma associated with hormonal contraceptive use, adjusting for potential confounders.
  
  
  RESULTS
  We identified 317 cases and 2126 controls. Ever use of hormonal contraceptive was associated with an OR of 1.5 (95% CI 1.2, 2.0) and the OR increased with duration of use (long term, ≥5 years: OR 1.9; 95% CI 1.2, 2.9). The association between long term hormonal contraceptive use and glioma risk was most pronounced for progestagen only therapy (OR 2.4; 95% CI 1.1, 5.1), especially when this regimen constituted the sole hormonal contraceptive therapy (OR 4.1; 95% CI 0.8, 20.8).
  
  
  CONCLUSIONS
  Long term hormonal contraceptive use may increase the risk of glioma.
authors.affiliation: Department of Neurology, Odense University Hospital, Sdr. Boulevard 29, 5000, Odense, Denmark; Institute of Clinical Research, Faculty of Health Sciences, University of Southern Denmark, Sdr. Boulevard 29, 5000, Odense, Denmark.
authors.forename: Lene
authors.initials: L
authors.lastname: Andersen
authors.forename: Søren
authors.initials: S
authors.lastname: Friis
authors.forename: Jesper
authors.initials: J
authors.lastname: Hallas
authors.forename: Pernille
authors.initials: P
authors.lastname: Ravn
authors.forename: Bjarne W
authors.initials: BW
authors.lastname: Kristensen
authors.forename: David
authors.initials: D
authors.lastname: Gaist
mesh_terms: D000293:Adolescent; D000328:Adult; D001932:Brain Neoplasms / Q000139:chemically induced* / Q000453:epidemiology; D016022:Case-Control Studies; D003278:Contraceptives, Oral, Hormonal / Q000009:adverse effects*; D003718:Denmark / Q000453:epidemiology; D005260:Female; D005910:Glioma / Q000139:chemically induced* / Q000453:epidemiology; D006801:Humans; D008875:Middle Aged; D016017:Odds Ratio; D012306:Risk; D055815:Young Adult
chemical_list: D003278:Contraceptives, Oral, Hormonal
keywords: brain tumour epidemiology; case-control study; glioma; hormonal contraceptive; risk