Lower risk for recurrent venous thrombosis in women explained by sex-specific risk factors

Men’s increased lifetime risk for recurrence of venous thrombosis may be explained by the younger age of women at time of first venous thrombosis and longer intervals between a provoked first episode and recurrence, according to recently published data.

Researchers retrospectively analyzed data from 523 women and 293 men from a cohort of families with thrombophilia.

The mean age of women at the time of first event was 34 vs. 44 in men (P<.001). Twenty-five percent of first events were unprovoked in women vs. 74% in men (P<.001).

Women were aged 40 at the time of recurrence while men were aged 48 (P<.001). The overall risk for recurrence was 5.1% per year (95% CI, 4.4-5.8) in women and 9.3% per year (95% CI, 7.8-10.9) in men, according to researchers. Compared with women, men had a crude RR for recurrence of 1.7 (95% CI, 1.4-2.1).

Among those with unprovoked first venous thrombosis and recurrence, crude RR was 1.2 (95% CI, 0.8-1.7), and age was comparable between men and women at both first venous thrombosis (46 years vs. 44 years; P=.38) and recurrence (49 years vs. 50 years; P=.60).

The median interval between end of anticoagulant treatment for first event and recurrence was 10.4 years in women with a hormonal first event vs. only 2.7 years in men (P<.001). Researchers noted that the longer interval was likely due to hormonal risk factors, as when only unprovoked events were considered, this difference did not remain (P=.94).

Men had a higher recurrence rate (45%) than women (31%) within the first two years after anticoagulation treatment (P=.011). Ten years after anticoagulation treatment, 30% of women had a recurrent event vs. 17% of men (P=.012).

In participants aged younger than 55 at first event, the adjusted RR was 1.6 (95% CI, 1.3-2.1) in men. Men were aged 45, and women were aged 38 at recurrence (P<.001).

Lijfering WM. Blood. 2009;doi:10.1182/blood-2009-04-205418.