title: Do racial differences exist in the association between pregnancy-induced hypertension and breast cancer risk?
abstract: BACKGROUND
  Previous studies investigating the relationship between pregnancy-induced hypertension (PIH) and breast cancer risk have yielded inconsistent results. Unlike numerous Western studies, studies have reported that PIH may be a risk factor for breast cancer in Western Asian women. To confirm these results, we designed a retrospective population-based cohort study to assess the relationship between PIH and subsequent risk for breast cancer in Taiwan.
  
  
  METHODS
  Patients with newly diagnosed PIH were selected from the Taiwan National Health Insurance Research Database (NHIRD), and a 1:4 matched cohort of women without PIH based on age and the year of delivery was randomly selected from the same database as the comparison group. The incidence of new-onset breast cancer was assessed in both cohorts.
  
  
  RESULTS
  Among the 23.3 million individuals registered in the NHIRD, 26,638 patients with PIH and 106,552 matched controls were identified. The incidence rate of breast cancer was higher in patients with PIH than in the matched controls (incidence rate ratio = 1.09, 95% confidence interval [CI] = 1.09-1.10, p < 0.0001). However, the Kaplan-Meier analysis revealed a similar cumulative incidence rate of breast cancer between the PIH and comparison cohorts (log-rank p = 0.4303). Moreover, results from a multivariate analysis indicated that PIH was not a statistically significant independent risk factor for breast cancer (adjusted hazard ratio = 1.10, 95% CI = 0.87-1.39, p = 0.4247).
  
  
  CONCLUSIONS
  The present study demonstrated no significant temporal relationship between PIH and risk for subsequent breast cancer in Eastern Asian women.
authors.affiliation: a Department of Obstetrics and Gynecology , Kaohsiung Veterans General Hospital , Kaohsiung , Taiwan.|b Department of Biological Science , National Sun Yat-sen University , Kaohsiung , Taiwan.|c School of Medicine , National Yang-Ming University , Taipei , Taiwan.
authors.forename: Li-Te
authors.initials: LT
authors.lastname: Lin
authors.affiliation: c School of Medicine , National Yang-Ming University , Taipei , Taiwan.|d Department of Psychiatry , Kaohsiung Veterans General Hospital , Kaohsiung , Taiwan.
authors.forename: Li-Yu
authors.initials: LY
authors.lastname: Hu
authors.affiliation: e Research Center of Medical Informatics , Kaohsiung Veterans General Hospital , Kaohsiung , Taiwan.|f College of Nursing , Kaohsiung Medical University , Kaohsiung , Taiwan.|g Department of Nursing , Meiho University , Ping-Tung , Taiwan.
authors.forename: Pei-Ling
authors.initials: PL
authors.lastname: Tang
authors.affiliation: a Department of Obstetrics and Gynecology , Kaohsiung Veterans General Hospital , Kaohsiung , Taiwan.|b Department of Biological Science , National Sun Yat-sen University , Kaohsiung , Taiwan.|c School of Medicine , National Yang-Ming University , Taipei , Taiwan.
authors.forename: Kuan-Hao
authors.initials: KH
authors.lastname: Tsui
authors.affiliation: b Department of Biological Science , National Sun Yat-sen University , Kaohsiung , Taiwan.
authors.forename: Jiin-Tsuey
authors.initials: JT
authors.lastname: Cheng
authors.affiliation: c School of Medicine , National Yang-Ming University , Taipei , Taiwan.|h Critical Care Center and Cardiovascular Medical Center , Kaohsiung Veterans General Hospital , Kaohsiung , Taiwan.|i Department of Physical Therapy , Fooyin University , Kaohsiung , Taiwan.
authors.forename: Wei-Chun
authors.initials: WC
authors.lastname: Huang
authors.affiliation: j Department of Surgery , Kaohsiung Veterans General Hospital , Kaoh , Taiwan.|k College of Management National Sun Yat-sen University , General Hospital, Kaohsiung , Taiwan.
authors.forename: Hong-Tai
authors.initials: HT
authors.lastname: Chang
mesh_terms: D000328:Adult; D001943:Breast Neoplasms / Q000208:ethnology*; D005260:Female; D006801:Humans; D046110:Hypertension, Pregnancy-Induced / Q000208:ethnology*; D011247:Pregnancy; D012189:Retrospective Studies; D013624:Taiwan / Q000453:epidemiology
keywords: Breast cancer; epidemiology; gestational hypertension; preeclampsia; pregnancy-induced hypertension