title: Migraine and breast cancer risk: a prospective cohort study and meta-analysis.
abstract: BACKGROUND
  The evidence for an association between migraine and breast cancer risk is inconclusive. While female sex hormones have been proposed as one underlying mechanism, data on sex hormone levels in migraineurs are sparse.
  
  
  METHODS
  We prospectively evaluated the association between migraine and breast cancer risk among 115378 Nurses' Health Study II participants using Cox proportional hazards models. Differences in endogenous sex hormone levels according to migraine status were assessed among 2034 premenopausal women using linear regression. We performed a meta-analysis of studies investigating the association between migraine and invasive breast cancer risk published through October 2013. All statistical tests were two-sided.
  
  
  RESULTS
  Seventeen thousand six hundred ninety-six women (15.3%) reported a physician's diagnosis of migraine at baseline. Over 20 years of follow-up, 833 in situ and 3091 invasive breast malignancies occurred. Migraine was not associated with total (hazard ratio [HR] = 0.96, 95% confidence interval [CI] = 0.88 to 1.04), in situ (HR = 0.97, 95% CI = 0.82 to 1.15), or invasive breast cancer risk (HR = 0.95, 95% CI = 0.87 to 1.04). Endogenous sex hormone levels did not differ according to migraine status. In the meta-analysis, migraine was associated with a lower risk of breast cancer overall (pooled risk ratio [RR] = 0.84, 95% CI = 0.73 to 0.98). However, this inverse association was apparent only among case-control studies (pooled RR = 0.72, 95% CI = 0.66 to 0.79), and not among cohort studies (pooled RR = 0.98, 95% CI = 0.87 to 1.10).
  
  
  CONCLUSIONS
  In this large cohort study, migraine was not associated with breast cancer risk or differences in endogenous sex hormone levels. While case-control studies suggest an inverse association between migraine and breast cancer risk, prospective cohort studies do not support an association in pooled analyses.
authors.affiliation: Division of Public Health Sciences, Department of Surgery, Washington University School of Medicine, St. Louis, MO (ACW); Channing Division of Network Medicine, Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, MA (MSR, RTF, AHE, RMT); Department of Epidemiology, Harvard School of Public Health, Boston, MA (MSR, RTF, AHE, RMT); Division of Preventive Medicine, Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, MA (TK); Team Neuroepidemiology, INSERM ​Research Center for Epidemiology and Biostatistics (U897), Bordeaux, France (TK); University of Bordeaux, Bordeaux, France (TK).
authors.forename: Anke C
authors.initials: AC
authors.lastname: Winter
authors.affiliation: Division of Public Health Sciences, Department of Surgery, Washington University School of Medicine, St. Louis, MO (ACW); Channing Division of Network Medicine, Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, MA (MSR, RTF, AHE, RMT); Department of Epidemiology, Harvard School of Public Health, Boston, MA (MSR, RTF, AHE, RMT); Division of Preventive Medicine, Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, MA (TK); Team Neuroepidemiology, INSERM ​Research Center for Epidemiology and Biostatistics (U897), Bordeaux, France (TK); University of Bordeaux, Bordeaux, France (TK).
authors.forename: Megan S
authors.initials: MS
authors.lastname: Rice
authors.affiliation: Division of Public Health Sciences, Department of Surgery, Washington University School of Medicine, St. Louis, MO (ACW); Channing Division of Network Medicine, Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, MA (MSR, RTF, AHE, RMT); Department of Epidemiology, Harvard School of Public Health, Boston, MA (MSR, RTF, AHE, RMT); Division of Preventive Medicine, Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, MA (TK); Team Neuroepidemiology, INSERM ​Research Center for Epidemiology and Biostatistics (U897), Bordeaux, France (TK); University of Bordeaux, Bordeaux, France (TK).
authors.forename: Renée T
authors.initials: RT
authors.lastname: Fortner
authors.affiliation: Division of Public Health Sciences, Department of Surgery, Washington University School of Medicine, St. Louis, MO (ACW); Channing Division of Network Medicine, Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, MA (MSR, RTF, AHE, RMT); Department of Epidemiology, Harvard School of Public Health, Boston, MA (MSR, RTF, AHE, RMT); Division of Preventive Medicine, Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, MA (TK); Team Neuroepidemiology, INSERM ​Research Center for Epidemiology and Biostatistics (U897), Bordeaux, France (TK); University of Bordeaux, Bordeaux, France (TK).
authors.forename: A Heather
authors.initials: AH
authors.lastname: Eliassen
authors.affiliation: Division of Public Health Sciences, Department of Surgery, Washington University School of Medicine, St. Louis, MO (ACW); Channing Division of Network Medicine, Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, MA (MSR, RTF, AHE, RMT); Department of Epidemiology, Harvard School of Public Health, Boston, MA (MSR, RTF, AHE, RMT); Division of Preventive Medicine, Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, MA (TK); Team Neuroepidemiology, INSERM ​Research Center for Epidemiology and Biostatistics (U897), Bordeaux, France (TK); University of Bordeaux, Bordeaux, France (TK).
authors.forename: Tobias
authors.initials: T
authors.lastname: Kurth
authors.affiliation: Division of Public Health Sciences, Department of Surgery, Washington University School of Medicine, St. Louis, MO (ACW); Channing Division of Network Medicine, Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, MA (MSR, RTF, AHE, RMT); Department of Epidemiology, Harvard School of Public Health, Boston, MA (MSR, RTF, AHE, RMT); Division of Preventive Medicine, Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, MA (TK); Team Neuroepidemiology, INSERM ​Research Center for Epidemiology and Biostatistics (U897), Bordeaux, France (TK); University of Bordeaux, Bordeaux, France (TK).
authors.forename: Rulla M
authors.initials: RM
authors.lastname: Tamimi
mesh_terms: D000328:Adult; D000368:Aged; D001943:Breast Neoplasms / Q000453:epidemiology* / Q000209:etiology / Q000517:prevention & control; D016022:Case-Control Studies; D015331:Cohort Studies; D005260:Female; D005500:Follow-Up Studies; D012739:Gonadal Steroid Hormones / Q000097:blood*; D006801:Humans; D008875:Middle Aged; D008881:Migraine Disorders / Q000150:complications / Q000453:epidemiology*; D009726:Nurses / Q000706:statistics & numerical data; D016017:Odds Ratio; D017697:Premenopause / Q000097:blood; D016016:Proportional Hazards Models; D011446:Prospective Studies; D018570:Risk Assessment; D012307:Risk Factors; D014481:United States / Q000453:epidemiology
chemical_list: D012739:Gonadal Steroid Hormones