title: Postmenopausal hormone replacement therapy and risk of cholecystectomy: a prospective cohort study.
abstract: OBJECTIVE
  Our aim of this study was to examine the association between the use of postmenopausal HRT and risk of cholecystectomy in Sweden, where the most common regimen of HRT (oral oestradiol in combination with testosterone-like progestin) has been different from those investigated in previous studies.
  
  
  METHODS
  We performed a prospective study of 27 892 postmenopausal women (aged 48-83 years) from the population-based Swedish Mammography Cohort. Use of HRT was assessed by a self-reported questionnaire at baseline in 1997, and the cohort was followed up through 2011 for procedures of cholecystectomy by linkage to the Swedish Patient Register. Cox proportional hazard models were used to estimate hazard ratios (HR) and 95% confidence intervals (CI).
  
  
  RESULTS
  During 362 728 person-years of follow-up (median 14 years), 995 cases of cholecystectomy were recorded. After adjustment for potential confounders, the HR of cholecystectomy was 1.52 (95% CI, 1.33-1.74) among ever users of HRT compared with never users. The risk did not differ by current or past use (p = 0.38) or duration of use (p = 0.65), but it did differ by indication of use (p = 0.006). Women who used HRT for systemic symptoms had a higher risk of cholecystectomy than those who used it for local symptoms (HR, 1.62; 95% CI, 1.41-1.87 vs HR, 1.21; 95% CI, 0.97-1.50).
  
  
  CONCLUSIONS
  This prospective study of postmenopausal women adds to the evidence that use of HRT may increase the risk of cholecystectomy.
authors.affiliation: Department of Molecular Medicine and Surgery, Karolinska Institutet , Stockholm , Sweden.
authors.forename: Caroline
authors.initials: C
authors.lastname: Nordenvall
authors.forename: Viktor
authors.initials: V
authors.lastname: Oskarsson
authors.forename: Omid
authors.initials: O
authors.lastname: Sadr-Azodi
authors.forename: Nicola
authors.initials: N
authors.lastname: Orsini
authors.forename: Alicja
authors.initials: A
authors.lastname: Wolk
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D002763:Cholecystectomy / Q000706:statistics & numerical data*; D002764:Cholecystitis / Q000453:epidemiology / Q000601:surgery*; D002769:Cholelithiasis / Q000453:epidemiology / Q000601:surgery*; D015914:Estrogen Replacement Therapy / Q000009:adverse effects* / Q000706:statistics & numerical data; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008875:Middle Aged; D017698:Postmenopause; D016016:Proportional Hazards Models; D011446:Prospective Studies; D018570:Risk Assessment; D013548:Sweden / Q000453:epidemiology