Venous Thromboembolism and Varicose Veins Share Familial Susceptibility: A Nationwide Family Study in Sweden

Abstract

Background Varicose veins ( VV s) 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 VV s. Methods and 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 [ SIR s]) of VTE and VV s were examined in 2 ways (ie, bidirectionally): risk of VTE in subjects whose siblings had been diagnosed with VV s and risk of VV s 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 VV s and 87 564 had VTE . An increased risk of VTE was observed in persons whose siblings had VV s ( SIR 1.30, 95% CI 1.26 to 1.33), whereas persons whose siblings had VTE had an increased risk of VV s ( SIR 1.30, 95% CI 1.27 to 1.34). If 2 or more siblings were affected by VTE , the risk for VV s was 1.70 (95% CI 1.53 to 1.88). Conversely, if 2 or more siblings were affected by VV s, the risk for VTE was 1.52 (95% CI 1.38 to 1.67). In spouses of VTE patients, a minor increased risk of VV s 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 VV s and VTE share familial susceptibility. This novel finding suggests the existence of shared familial and possibly genetic factors.