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

BackgroundData 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). MethodsWe linked Multigeneration Register data on individuals aged 0-77years to the Swedish nationwide Hospital Discharge Register 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 (HRs) to determine the familial HR for recurrent hospitalization for VTE. Results and ConclusionsThe 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%CI1.14-1.49) for those with affected siblings. The risk of recurrent VTE hospitalization in individuals with two affected parents was 1.92 (95%CI1.44-2.58). 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.