title: Venous thromboembolism and varicose veins share familial susceptibility: a nationwide family study in Sweden.
abstract: BACKGROUND
  Varicose veins (VVs) have been associated with venous thromboembolism (VTE), but whether these diseases share familial susceptibility has not been determined. This nationwide study aimed to determine whether VTE shares familial susceptibility with VVs.
  
  
  RESULTS
  Swedish Multigeneration Register data for persons aged 0 to 76 years during the period 1964-2008 were linked to the Swedish Inpatient and Outpatient Registers. Familial risks (standardized incidence ratios [SIRs]) of VTE and VVs were examined in 2 ways (ie, bidirectionally): risk of VTE in subjects whose siblings had been diagnosed with VVs and risk of VVs in persons whose siblings had been diagnosed with VTE. The analyses were repeated for spouses to determine the importance of shared adult family environment. In total, 96 810 siblings had VVs and 87 564 had VTE. An increased risk of VTE was observed in persons whose siblings had VVs (SIR 1.30, 95% CI 1.26 to 1.33), whereas persons whose siblings had VTE had an increased risk of VVs (SIR 1.30, 95% CI 1.27 to 1.34). If 2 or more siblings were affected by VTE, the risk for VVs was 1.70 (95% CI 1.53 to 1.88). Conversely, if 2 or more siblings were affected by VVs, the risk for VTE was 1.52 (95% CI 1.38 to 1.67). In spouses of VTE patients, a minor increased risk of VVs was observed (SIR 1.05 for husbands, SIR 1.06 for wives). The risk of VTE in spouses of VV patients was similarly small (SIR 1.01 for husbands, SIR 1.05 for wives).
  
  
  CONCLUSIONS
  VVs and VTE share familial susceptibility. This novel finding suggests the existence of shared familial and possibly genetic factors.
authors.affiliation: Center for Primary Health Care Research, Lund University/Region Skåne, Malmö, Sweden (B., J.J., J.S., K.S.).
authors.forename: Bengt
authors.initials: B
authors.lastname: Zöller
authors.affiliation: Center for Primary Health Care Research, Lund University/Region Skåne, Malmö, Sweden (B., J.J., J.S., K.S.).
authors.forename: Jianguang
authors.initials: J
authors.lastname: Ji
authors.affiliation: Center for Primary Health Care Research, Lund University/Region Skåne, Malmö, Sweden (B., J.J., J.S., K.S.) Stanford Prevention Research Centre, Stanford University School of Medicine, Stanford, CA (J.S., K.S.).
authors.forename: Jan
authors.initials: J
authors.lastname: Sundquist
authors.affiliation: Center for Primary Health Care Research, Lund University/Region Skåne, Malmö, Sweden (B., J.J., J.S., K.S.) Stanford Prevention Research Centre, Stanford University School of Medicine, Stanford, CA (J.S., K.S.).
authors.forename: Kristina
authors.initials: K
authors.lastname: Sundquist
mesh_terms: D000328:Adult; D005260:Female; D020022:Genetic Predisposition to Disease; D006801:Humans; D008297:Male; D008875:Middle Aged; D012042:Registries; D035781:Siblings; D012923:Social Class; D018454:Spouses; D013548:Sweden / Q000453:epidemiology; D014648:Varicose Veins / Q000453:epidemiology* / Q000235:genetics; D054556:Venous Thromboembolism / Q000453:epidemiology* / Q000235:genetics
keywords: embolism; epidemiology; genetics; thrombosis; veins