Thromboembolism during hormone therapy in Japanese women

Japanese women are unaccustomed to taking hormone therapies such as oral contraceptives (OCs) and hormone replacement therapy (HRT); therefore, there are few studies associated with hormone treatment in Japan. This study focused on evaluating thromboembolism during hormone therapy in Japanese women. In February 2002, we mailed questionnaires regarding the monthly average number of patients who had received prescriptions for OCs and HRT, and the incidence of arterial and venous thromboemboli during hormone therapy for the last 10 years. The mailings were sent to hospitals and clinics that are registered as monitoring institutions with the Japan Association of Obstetricians and Gynecologists. Of 1083 institutes, 771 responded (71% response rate). In July 2002, to obtain additional information on hormone therapy, patient history, and outcomes, we sent follow-up questionnaires to 39 institutions that responded as having experienced cases of thromboembolism. Thirty-nine institutions (5.1% of institutions responding to survey) experienced 53 cases of thromboembolism during hormone therapy. The 53 patients included 29 who received OCs (OC patients), 13 who received HRT (HRT patients), and 11 who received other hormone treatment. Among the 29 OC patients, eight had been diagnosed as having arterial thromboembolism (ATE), including two patients with myocardial infarction (MI) and six with ischemic stroke, whereas 20 had venous thromboembolism (VTE), including two with pulmonary embolism (PE) The remaining patient had an unknown thromboembolic event. Of the OC patients, 75.9% had a thromboembolism within the first year, and 58.6% patients were in their 40s. In 13 HRT patients, seven had ATE, including two MI patients and three with ischemic brain stroke, whereas six had VTE, including one PE patient. The duration of HRT varied widely from less than 1 year to more than 3 years; moreover, the HRT type did not affect thromboembolism occurrence. More than 70% of ATE patients and less than one third of VTE patients had to be hospitalized for the treatment of thromboembolism, and more than 75% of VTE patients recovered completely. However, one third of the ATE patients recovered with mild sequelae, one OC patient had severe sequelae due to stroke, and another OC patient died due to an ischemic event. The estimated incidence of thromboembolism in OC patients and HRT patients was 3.6 to 14.4 and 1.7 to 3.4 per 100,000 woman-years, respectively. The risk factors of thromboembolism, which were found consistently in this study, included obesity, smoking, lifestyle, and aging. Approximately 95% of institutions had not experienced thromboembolism in their hormone therapy patients, suggesting the incidence of thromboembolism during hormone therapy might be low. However, according to an analysis of risk factors, screening users of hormone supplements may be essential for providing safe hormone therapy. Moreover, because of the early occurrence of thromboembolism during hormone therapy, especially with OCs, it is important to monitor and instruct patients with caution from immediately after therapy initiation.