Hormonal factors and risk of recurrent venous thrombosis: the prevention of recurrent venous thromboembolism trial

Thrombosis and antithrombotic therapy in women

Sex-based differences in the prevalence and presentation of arterial and venous thrombosis exist, and emerging data indicate that men and women do not accrue equal benefit from antithrombotic therapy. Sex hormones alter procoagulant protein expression and the function of blood and vascular cells. Sex-based differences in platelet function have been reported, and in animal models, sex-based differences in thrombosis have been noted. Here we review plausible mechanisms that may explain how sex functions as a modifier of thrombosis and summarize clinical data on the interaction between sex and response to antithrombotic therapy.

[Optimum duration of anticoagulant treatment after an episode of venous thromboembolism]

Vitamin K antagonists are the mainstay for the treatment for venous thromboembolism. The optimum (VTE) course of oral anticoagulant therapy is determined according to the risk of recurrent VTE after stopping anticoagulant therapy and the risk of anticoagulant-related bleeding while on antivitamin K. The risk of recurrent VTE is low when the initial episode is provoked by a reversible major-risk factor (surgery), whereas this risk is high when VTE is not provoked or associated with a persistent-risk factor (cancer). Conversely, the influence of biochemical and morphological tests is uncertain. The optimum balance of the benefits and the risks of oral anticoagulant therapy is based on the frequency as well as the consequences of the risk of recurrent VTE and anticoagulant-related bleeding. After VTE provoked by a major reversible-risk factor, three months of anticoagulation is optimal, whereas after unprovoked VTE, anticoagulation should be extended. However, given the number of unresolved issues, a randomised trial comparing different durations of anticoagulation is needed.

Venous thromboembolism in women

Abstract

The risk of venous thromboembolism (VTE) varies throughout a woman’s life and is associated primarily with underlying hormonal exposure. Alteration in hemostatic mechanisms, including resistance to activated protein C, may explain this altered risk. Initially, development of VTE with the use of contraception in young adulthood may reveal inherited thrombophilia. Pregnancy, and particularly the post-partum period, likely confer the greatest risk of VTE, but the absolute risk is small. Guidelines for prevention of VTE during pregnancy are based on personal or family history of VTE, and known inherited thrombophilia. Use of hormone replacement therapy later in life is associated with increased risk of VTE, and may be safest if given as an estrogen-only preparation to young postmenopausal women for less than 5 years. Universal screening for thrombophilia prior to pregnancy or initiating hormonal therapy is not recommended; however, selected testing in high-risk groups may be warranted. The lack of firm recommendations for the prevention of VTE in women highlights the need for future investigation aimed at identifying high-risk groups and evaluating the efficacy of prophylactic measures.

The effects of race/ethnicity and sex on the risk of venous thromboembolism

PURPOSE OF THE REVIEW

Recently, studies on large diverse populations have described important ethnic/racial differences in venous thromboembolism incidence, and sex has been reported as an important predictor of recurrence. We review the influence of race/ethnicity and sex on venous thromboembolism, concentrating on articles from 2005 to 2007.

RECENT FINDINGS

Most studies found that women have a 40-400% lower risk of recurrent venous thromboembolism than men. Studies of ethnicity/race on risk provide strong evidence that African-American patients are the highest risk group for first-time venous thromboembolism, while Hispanic patients' risk is about half that of Caucasians. African-Americans and Hispanics have a higher risk of recurrence than Caucasians, but sex and the type of index venous thromboembolism event seem to play a role in this risk. Asian/Pacific Islanders have a markedly lower risk of first-time and cancer-associated venous thromboembolism. There is little difference in incidence in African-Americans, Hispanics, and Caucasians diagnosed with cancer. Sex does not seem to be associated with risk in cancer patients.

SUMMARY

Sex and race/ethnicity are important factors in the risk of first-time and recurrent venous thromboembolism and need to be included as risk assessment and diagnostic prediction tools are developed or updated.

Epidemiology and risk factors for venous thrombosis

Venous thrombosis, including deep vein thrombosis (DVT) and pulmonary embolism (PE), occurs at an annual incidence of about 1 per 1,000 adults. Rates increase sharply after about age 45 years, and are slightly higher in men than women in older age. Major risk factors for thrombosis, other than age, include exogenous factors such as surgery, hospitalization, immobility, trauma, pregnancy, and the puerperium and hormone use, and endogenous factors such as cancer, obesity, and inherited and acquired disorders of hypercoagulation. This review focuses on epidemiology of venous thrombosis and the general implications of this in patient management.