title: Associations between Medical Conditions and Breast Cancer Risk in Asians: A Nationwide Population-Based Study in Taiwan.
abstract: BACKGROUND
  The breast cancer incidence in Asia is rising. To explore whether the etiology of breast cancer is different from the known risk factors from studies in Western countries, we conducted a nested case-control study using data from the Taiwan National Health Insurance Research Database (NHIRD).
  
  
  METHODS
  All medical conditions based on the first three digits of the ICD-9 and a list of medical conditions based on literature review were retrieved for each case and control. The odds ratios (OR) and 95% confidence intervals (CI) of the associations between medical conditions and breast cancer risks were estimated using conditional logistic regression and adjusted for occupation, number of breast cancer screening, and the average number of outpatient visits prior the diagnosis. The associations were also estimated for younger (<50 years old) and older subjects separately.
  
  
  RESULTS
  The analyses included 4,884 breast cancer cases and 19,536 age-matched controls. Prior breast diseases (OR, 95% CI: 2.47, 2.26-2.71), obesity (1.43, 1.04-1.96), endometriosis (1.44, 1.15-1.80), uterine leiomyoma (1.20, 1.03-1.40), hypertensive diseases (1.14, 1.05-1.25), and disorders in lipid metabolism (1.13, 1.04-1.24) were associated with increased breast cancer risk. No heterogeneity was observed between age groups (<50 and ≥50 years old).
  
  
  CONCLUSIONS
  In addition to benign breast diseases, obesity, endometriosis, uterine leiomyoma, hypertensive diseases, and disorders of lipid metabolism were associated with a subsequent breast cancer risk.
  
  
  CONCLUSIONS
  Our results suggest that estrogen related factors may play an important role in breast cancer risks in the Taiwanese female population.
authors.affiliation: Institute of Population Health Sciences, National Health Research Institutes, Miaoli, Taiwan.
authors.forename: Shu-Chun
authors.initials: SC
authors.lastname: Chuang
authors.affiliation: Institute of Population Health Sciences, National Health Research Institutes, Miaoli, Taiwan.
authors.forename: Guo-Jie
authors.initials: GJ
authors.lastname: Wu
authors.affiliation: Department of Oncology, National Taiwan University Hospital, Taipei, Taiwan.|Department of Internal Medicine, National Taiwan University Hospital, Taipei, Taiwan.
authors.forename: Yen-Shen
authors.initials: YS
authors.lastname: Lu
authors.affiliation: Department of Oncology, National Taiwan University Hospital, Taipei, Taiwan.
authors.forename: Ching-Hung
authors.initials: CH
authors.lastname: Lin
authors.affiliation: Institute of Population Health Sciences, National Health Research Institutes, Miaoli, Taiwan.
authors.forename: Chao Agnes
authors.initials: CA
authors.lastname: Hsiung
mesh_terms: D000328:Adult; D000368:Aged; D044466:Asian People; D001943:Breast Neoplasms / Q000453:epidemiology* / Q000209:etiology*; D016022:Case-Control Studies; D002908:Chronic Disease / Q000453:epidemiology; D015897:Comorbidity; D005260:Female; D006304:Health Status; D006801:Humans; D008875:Middle Aged; D011159:Population Surveillance; D012306:Risk; D013624:Taiwan / Q000453:epidemiology; D055815:Young Adult