title: Hormonal factors and risk of recurrent venous thrombosis: the prevention of recurrent venous thromboembolism trial.
abstract: BACKGROUND
  In some but not all studies, men with venous thrombosis had a higher risk of recurrence than women. Information on women with initial hormone-related thrombosis is scant.
  
  
  OBJECTIVE
  We assessed the incidence of recurrent thrombosis by gender, and among women using exogenous hormones or pregnant/postpartum at the time of index thrombosis.
  
  
  METHODS
  A total of 508 men and women with one or more previous venous thrombosis episodes were observed while participating in a randomized trial of low-intensity warfarin or placebo for 2.1 years. Index thrombosis events during treatment with postmenopausal hormones, oral contraceptives, or during pregnancy, or the puerperium were considered to be hormone-related events.
  
  
  RESULTS
  Among 268 men the 3-year probability of recurrent thrombosis was 18.4% (95% confidence intervals; CI 12.3-24.4). Among 109 women without hormone-related thrombosis, the rate was 15.0% (95% CI 6.3-23.8). Among 129 women with hormone-related thrombosis, the rate was 5.0% (95% CI 1.1-8.9). Adjusting for other risk factors and treatment assignment, women had a 39% lower thrombosis recurrence risk than men: hazard ratio (HR) 0.61 (95% CI 0.34-1.08). Women with hormone-related thrombosis had a 58% lower risk than men: HR 0.42 (95% CI 0.19-0.97); and a 46% lower recurrence risk than other women; HR 0.54 (95% CI 0.19-1.54). Women without hormone-related index events had a recurrence rate similar to men; HR 0.83 (95% CI 0.42-1.66).
  
  
  CONCLUSIONS
  In this trial population, women had a lower risk of recurrent venous thrombosis than men. This difference was explained by a low risk of recurrence among women with hormone-related index thrombosis.
authors.affiliation: Department of Medicine, University of Vermont, Burlington, VT 05446, USA. mary.cushman@uvm.edu
authors.forename: M
authors.initials: M
authors.lastname: Cushman
authors.forename: R J
authors.initials: RJ
authors.lastname: Glynn
authors.forename: S Z
authors.initials: SZ
authors.lastname: Goldhaber
authors.forename: S
authors.initials: S
authors.lastname: Moll
authors.forename: K A
authors.initials: KA
authors.lastname: Bauer
authors.forename: S
authors.initials: S
authors.lastname: Deitcher
authors.forename: S
authors.initials: S
authors.lastname: Shrivastava
authors.forename: P M
authors.initials: PM
authors.lastname: Ridker
mesh_terms: D000368:Aged; D000925:Anticoagulants / Q000627:therapeutic use*; D005260:Female; D006728:Hormones / Q000378:metabolism*; D006801:Humans; D019934:International Normalized Ratio; D008297:Male; D008875:Middle Aged; D015233:Models, Statistical; D010919:Placebos; D012008:Recurrence; D012306:Risk; D012307:Risk Factors; D012737:Sex Factors; D013923:Thromboembolism / Q000453:epidemiology / Q000378:metabolism* / Q000473:pathology*; D020246:Venous Thrombosis / Q000453:epidemiology / Q000378:metabolism* / Q000473:pathology*; D014859:Warfarin / Q000627:therapeutic use*
chemical_list: D000925:Anticoagulants; D006728:Hormones; D010919:Placebos; D014859:Warfarin