Familial Transmission of Venous Thromboembolism: A Cohort Study of 80,214 Swedish Adoptees Linked to Their Biological and Adoptive Parents
Background—Venous thromboembolism (VTE) clusters in families, but the familial risk of VTE has not been determined among adoptees. The aim was to disentangle the contributions of genetic and environmental factors to the familial transmission of VTE.
Methods and Results—The Swedish Multi-Generation register was used to follow all Swedish-born adoptees born 1932-2004 (n = 80,214) between January 1, 1964 and December 31, 2010 for VTE. The risk of VTE was estimated in adoptees with at least one biological parent with VTE compared with adoptees without a biological parent with VTE. The risk of VTE was also estimated in adoptees with at least one adoptive parent with VTE compared with adoptees without an adoptive parent with VTE. Adoptees with at least one biological parent with VTE (n = 137) were more likely to have VTE than adoptees without a biological parent with VTE (standardized incidence ratio=SIR) 1.51; 95% confidence interval 1.27-1.79. The SIR for VTE was highest for adoptees with a biological parent diagnosed with VTE before the age of 50 years (SIR=2.03, 1.24-3.14). In contrast, adoptees with at least one adoptive parent with VTE (n = 156) were not at increased risk of VTE (SIR=1.07, 0.91-1.25).
Conclusions—These novel findings suggest that genetic factors make a stronger contribution to the familial transmission of VTE from parents to offspring, than family environmental factors.
- Received August 23, 2013.
- Revision received March 12, 2014.
- Accepted March 25, 2014.