Summary
As homocysteine-lowering treatment has not reduced the risk of recurrent thrombosis
in recent clinical trials, we hypothesized that mild hyperhomocysteinaemia is an epiphenomenon
or associated with a low absolute risk of thrombosis. In this retrospective study,
we enrolled 478 evaluable first-degree relatives of consecutive patients with venous
thrombosis or premature atherosclerosis, and hyperhomocysteinemia. Absolute risks
of thrombosis and effects of concomitant thrombophilic defects were compared. Relative
risks were adjusted for clustering in families, age, sex, and atherosclerotic risk
factors, where appropriate. Annual incidence of venous thrombosis was 0.16% (95% confidence
interval [CI], 0.08–0.30) in hyperhomocysteinemic relatives versus 0.11% (CI, 0.05–0.20)
in normohomocysteinemic relatives; adjusted relative risk 1.6 (CI, 0.6–4.5). Annual
incidences of arterial thrombosis were 0.34% (CI, 0.21–0.52) and 0.24% (CI, 0.15–0.37)
in hyperhomocysteinemic and normohomocysteinemic relatives, respectively; adjusted
relative risk 1.5 (CI, 0.6–3.5). Concomitance of multiple thrombophilic risk factors
increased the risk of venous thrombosis in hyperhomocysteinemic relatives 20 fold,
but a comparable effect was demonstrated in normohomocysteinemic relatives. We conclude
that hyperhomocysteinaemia is associated with a low absolute risk of venous and arterial
thrombosis. Concomitant thrombophilic defects are probably main determinants on the
risk of venous thrombosis, rather than hyperhomocysteinaemia itself.
Keywords
Clinical studies - risk factors - venous thrombosis - arterial thrombosis - thrombophilia