Familial Transmission of Hospital-Treated Varicose Veins in Adoptees: A Swedish Family Study

Abstract

Varicose veins (VVs) cluster in families, but the familial risk of VVs has not been determined among adoptees. The aim was to estimate whether the familial transmission of VVs is related to disease in biological and/or adoptive parents. The Swedish Multi-Generation Register and the Swedish Patient Register were used to follow all Swedish-born adoptees (born 1932 through 2004) that could be linked to both their biological and their adoptive parents (n= 80,214; 50% females). The risk of VVs was estimated in adoptees with at least 1 biological parent with VVs, but no adoptive parent with VVs (n= 187) compared with adoptees without a biological or adoptive parent with VVs (n= 1,758). The risk of VVs was also determined in adoptees with at least 1 adoptive parent, but no biological parent with VVs (n= 87), and in adoptees with both biological and adoptive parents affected (n= 21). Adoptees from an affected biological parent, but no adoptive parent, were more likely to have VVs than adoptees from an unaffected biological or adoptive parent (standard incidence ratio [SIR]= 2.21; 95% CI, 1.91-2.55). The familial SIR for adoptees with both an affected biological parent and an adoptive parent was 4.58 (95% CI, 2.83-7.01). Adoptees with an affected adoptive parent but no biological parent were not at increased risk of VVs (SIR= 1.15; 95% CI, 0.92-1.42). These novel findings suggest that genetic factors make a strong contribution to the familial transmission of VVs from parents to offspring, although familial environmental factors might contribute.