title: Familial Clustering of Venous Thromboembolism - A Danish Nationwide Cohort Study.
abstract: BACKGROUND
  Identification of risk factors for venous thromboembolism (VTE) is of utmost importance to improve current prophylactic regimes and treatment guidelines. The extent to which a family history contributes to the risk of VTE needs further exploration.
  
  
  OBJECTIVE
  To examine the relative rate of VTE in first-degree relatives compared with the general population.
  
  
  METHODS
  By crosslinking Danish nationwide registries we identified patients with VTE between 1978 and 2012, and their familial relations. The first member in a family to acquire VTE was defined as the proband. All first-degree relatives to probands were followed from the VTE date of the proband and until an event (VTE), death, emigration, 100 year birthday or end of study: 31st of December 2012, whichever came first. The relative rate of VTE was estimated by standardized incidence ratios (SIR) using time-dependent Poisson regression models, with the general population as a fixed reference.
  
  
  RESULTS
  We identified 70,767 children of maternal probands, 66,065 children of paternal probands, and 29,183 siblings to sibling probands. Having a maternal proband or a paternal proband were associated with a significantly increased VTE rate of 2.15 (CI: 2.00-2.30) and 2.06 (CI: 1.92-2.21), respectively. The highest estimate of VTE was observed among siblings (adjusted SIR of 2.60 [CI: 2.38-2.83]). Noteworthy, the rate of VTE increased for all first-degree relatives when the proband was diagnosed with VTE in a young age (≤ 50 years).
  
  
  CONCLUSIONS
  A family history of VTE was associated with a significantly increased rate of VTE among first-degree relatives compared with the general population.
authors.affiliation: Department of Cardiology, Copenhagen University Hospital Herlev and Gentofte, Hellerup, Denmark.|Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen N, Denmark.
authors.forename: Caroline
authors.initials: C
authors.lastname: Sindet-Pedersen
authors.affiliation: Department of Cardiology, Copenhagen University Hospital Herlev and Gentofte, Hellerup, Denmark.|Institute of Health, Science and Technology, Aalborg University, Aalborg, Denmark.
authors.forename: Louise
authors.initials: L
authors.lastname: Bruun Oestergaard
authors.affiliation: Department of Cardiology, Copenhagen University Hospital Herlev and Gentofte, Hellerup, Denmark.
authors.forename: Anna
authors.initials: A
authors.lastname: Gundlund
authors.affiliation: The Danish Heart Foundation, Copenhagen K, Copenhagen, Denmark.|Department of Cardiology, Copenhagen University Hospital Rigshospitalet, Copenhagen Ø, Denmark.
authors.forename: Emil Loldrup
authors.initials: EL
authors.lastname: Fosbøl
authors.affiliation: Institute of Health, Science and Technology, Aalborg University, Aalborg, Denmark.|Department of Ophthalmology, Aalborg University Hospital, Aalborg, Denmark.
authors.forename: Kristian
authors.initials: K
authors.lastname: Aasbjerg
authors.affiliation: Department of Cardiology, Copenhagen University Hospital Herlev and Gentofte, Hellerup, Denmark.|Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen N, Denmark.
authors.forename: Jannik
authors.initials: J
authors.lastname: Langtved Pallisgaard
authors.affiliation: Department of Cardiology, Copenhagen University Hospital Herlev and Gentofte, Hellerup, Denmark.|The Danish Heart Foundation, Copenhagen K, Copenhagen, Denmark.|Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen N, Denmark.|The National Institute of Public Health, University of Southern Denmark, Odense, Denmark.
authors.forename: Gunnar
authors.initials: G
authors.lastname: Gislason
authors.affiliation: Department of Cardiology, Copenhagen University Hospital Herlev and Gentofte, Hellerup, Denmark.|Institute of Health, Science and Technology, Aalborg University, Aalborg, Denmark.
authors.forename: Christian
authors.initials: C
authors.lastname: Torp-Pedersen
authors.affiliation: Department of Cardiology, Copenhagen University Hospital Herlev and Gentofte, Hellerup, Denmark.
authors.forename: Jonas
authors.initials: J
authors.lastname: Bjerring Olesen
mesh_terms: D000328:Adult; D000368:Aged; D015331:Cohort Studies; D003718:Denmark / Q000453:epidemiology; D005260:Female; D006801:Humans; D015994:Incidence; D008297:Male; D008875:Middle Aged; D010375:Pedigree; D012307:Risk Factors; D054556:Venous Thromboembolism / Q000175:diagnosis / Q000453:epidemiology*