Family history of venous thromboembolism ( VTE ) and risk of recurrent hospitalization for VTE : a nationwide family study in S weden

Summary Background Data concerning the importance of a family history of venous thromboembolism ( VTE ) for the risk of recurrent VTE are sparse. The aim of this nationwide study was to determine whether a family history of VTE is a risk factor for recurrent hospitalization for unprovoked VTE (deep vein thrombosis of the lower extremities or pulmonary embolism). Methods We linked M ultigeneration Register data on individuals aged 0–77 years to the S wedish nationwide H ospital D ischarge R egister data for the period 1987–2009 to compare the risk of hospitalization for unprovoked recurrent VTE among individuals with and without a parental or sibling history of VTE . We calculated hazard ratios ( HR s) to determine the familial HR for recurrent hospitalization for VTE . Results and Conclusions The risk of recurrent VTE hospitalization was 1.20 (95% confidence interval [ CI ] 1.10–1.32) for individuals with affected parents, and 1.30 (95%  CI  1.14–1.49) for those with affected siblings. The risk of recurrent VTE hospitalization in individuals with two affected parents was 1.92 (95%  CI  1.44–2.58). There was an interaction between age at diagnosis of VTE and a family history of VTE , with a family history having a stronger effect on VTE risk in younger patients. We conclude that a family history of VTE is a modest risk factor for recurrent VTE hospitalization in Sweden.