title: Increased risk of multiple sclerosis among women with migraine in the Nurses' Health Study II.
abstract: BACKGROUND
  The prospective Nurses' Health Study II (NHS-II), which enrolled over 116,000 female nurses, provides a unique opportunity to test the hypothesis of whether migraine is associated with multiple sclerosis (MS) and to explore the temporal aspects of the interrelationship.
  
  
  OBJECTIVE
  To calculate relative risk of MS among NHS-II participants with and without migraine and to estimate odds ratio (OR) of being diagnosed with migraine in women with and without pre-existing MS.
  
  
  METHODS
  Cox proportional hazards regression was used to estimate rate ratios and 95% confidence intervals (CIs) of being diagnosed with MS in women with and without pre-existing migraine adjusted for potential confounders. Multivariate adjusted ORs of being diagnosed with migraine in women with and without pre-existing MS were estimated using logistic regression.
  
  
  RESULTS
  The prevalence of migraine in women with MS at baseline (26%, p = 0.11) and those diagnosed with MS after enrolment (29%, p < 0.0001) was higher than in the non-MS cases (21%). The relative risk of developing MS in migraineurs was 1.39 times higher than in non-migraineurs (95% CI 1.10-1.77, p = 0.008). The absolute risk of developing MS in women migraineurs over a 15-year follow-up was 0.47% and among non-migraineurs 0.32%. The odds of being diagnosed with migraine was higher in women with pre-existing MS compared with those without MS, but did not reach statistical significance (OR = 1.57, 95% CI 0.97-2.52; p = 0.06).
  
  
  CONCLUSIONS
  Using a large, cohort of women-nurses, history of migraine was associated with an increased risk of MS. However, the difference in absolute risk of MS in migraineurs and non-migraineurs was small.
authors.affiliation: MS Care Center, Department of Neurology, NYU School of Medicine, NY, USA. ilya.kister@gmail.com
authors.forename: Ilya
authors.initials: I
authors.lastname: Kister
authors.forename: Kassandra L
authors.initials: KL
authors.lastname: Munger
authors.forename: Joseph
authors.initials: J
authors.lastname: Herbert
authors.forename: Alberto
authors.initials: A
authors.lastname: Ascherio
mesh_terms: D000328:Adult; D015331:Cohort Studies; D005260:Female; D006801:Humans; D008881:Migraine Disorders / Q000150:complications*; D009103:Multiple Sclerosis / Q000150:complications / Q000453:epidemiology*; D009726:Nurses; D015995:Prevalence; D016016:Proportional Hazards Models; D012307:Risk Factors