ABSTRACT
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.
KEYWORDS
Oral contraceptives - hormone replacement therapy - myocardial infarction - ischemic
brain stroke - venous thromboembolism
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Tomoko AdachiM.D. Ph.D.
Department of Obstetrics and Gynecology, Aiiku Maternal and Child Health Center
Aiiku Hospital, 5-6-8 Minamiazabu, Minato-ku
Tokyo 106-8580, Japan
eMail: tadachi@obgy.twmu.ac.jp