Submitted April 7, 2009
Accepted June 25, 2009
A lower risk of recurrent venous thrombosis in women compared to men is explained by sex-specific risk factors at time of first venous thrombosis in thrombophilic families
Willem M. Lijfering*, Nic J.G.M. Veeger, Saskia Middeldorp, Karly Hamulyak, Martin H. Prins, Harry R. Buller, and Jan van der Meer
Division of Haemostasis, Thrombosis and Rheology, Department of Hematology, University Medical Center Groningen, Groningen, Netherlands
Department of Clinical Epidemiology, Leiden University Medical Center, Leiden, Netherlands
Department of Hematology, University Hospital Maastricht, Maastricht, Netherlands
Department of Clinical Epidemiology and Medical Technology Assessment, University Hospital Maastricht, Maastricht, Netherlands
Department of Vascular Medicine, Academic Medical Center, Amsterdam, Netherlands
* Corresponding author; email: w.lijfering{at}int.umcg.nl.
Why men appear to have an increased risk of recurrent venous thrombosis compared to women is unknown. In a cohort study of families with thrombophilia, life-time risk of recurrent venous thrombosis was assessed in men and women (n=816). Adjusted relative risk of recurrence was 1.6 (95% CI, 1.3-2.0) in men compared to women. Women were younger at time of their first event (mean 34 years vs 44 years, P<0.001) and at time of recurrence (40 years vs 48 years, P<0.001). After excluding provoked first and recurrent venous thrombosis, adjusted relative risk was 1.2 (95% CI, 0.8-1.7), while mean age at recurrence was comparable in men and women (50 years vs 49 years, P=0.595). In women with a hormonal first event, median interval between first event and recurrence was 10.4 years vs 2.7 years in men (P<0.001). This difference was not observed when only unprovoked events were considered (P=0.938). The difference in life-time risk of recurrent venous thrombosis between men and women in thrombophilic families can be explained by a younger age of women at time of first venous thrombosis due to hormonal risk factors, and a longer interval between a provoked first episode of venous thrombosis and recurrence in women.
