The epidemiological characteristics of thromboembolism related to oral contraceptives in Japan: Results of a national survey

Abstract

The aim of this study was to reveal the epidemiological characteristics of thromboembolism related to combined oral contraceptives (COCs) in Japan. A survey of confirmed thromboembolism patients among Japanese COC users was conducted at randomly selected hospitals from across Japan. The survey examined six types of venous thromboembolism (VTE) and arterial thromboembolism (ATE) in all COC users: pulmonary embolism, deep vein thrombosis, other venous thrombosis, cerebral infarction, myocardial infarction, and other arterial thrombosis. The survey covered 5 years from 2009 to 2013. This study was approved in an ethical review by Hamamatsu University School of Medicine. Four hundred and twenty-five cases clearly related to COCs were analyzed. The annual estimated incidence rates per 10 000 person-years of VTE, ATE and all thromboembolisms in all COC users were 1.17, 0.33 and 1.50, respectively. The incidence of thromboembolism was 35.2% within 30 days from the start of COCs, 53.8% within 90 days, 66.9% within 180 days and 78.2% within 360 days regardless of progestin type. Age adjusted odds ratios in the obese and underweight groups were 2.33 and 0.98 for overall thromboembolism, 2.59 and 0.77 for VTE, and 1.11 and 1.28 for ATE compared with the standard group, respectively. Odds ratios for thromboembolism in non-O blood groups were 1.89 for overall thromboembolism, 2.16 for VTE, and 1.35 for ATE, when compared with the O blood group. The epidemiological characteristics of COC-related thromboembolisms were revealed in this national survey covering the years from 2009 to 2013.