Increased risk of thromboembolism in adenomyosis: a case–control study

RESEARCH QUESTION: Does adenomyosis increase the risk of thromboembolic events, including both arterial and venous thromboembolism, compared with endometriosis, and what clinical factors may contribute to this association? DESIGN: This retrospective case-control study was conducted at the University of Tokyo Hospital. In total, 1826 symptomatic women were included, comprising 745 women diagnosed with adenomyosis and 1081 women with endometriosis without adenomyosis. To minimize confounding by age, an established risk factor for thromboembolism, 712 age-matched pairs were analysed. The prevalence and types of thromboembolic events were compared between groups, and clinical characteristics such as anaemia and oestrogen exposure were evaluated. RESULTS: A history of thromboembolism was identified in 2.7% (20/745) of patients with adenomyosis and 0.5% (5/1081) of patients with endometriosis (P < 0.001). After age adjustment, the difference remained significant (2.8% versus 0.7%; P = 0.005). Venous thromboembolism was more common in patients with adenomyosis than in patients with endometriosis (2.4% versus 0.7%; P = 0.019). Arterial thromboembolism occurred in the adenomyosis group alone (0.4%). Among patients with adenomyosis with a history of thromboembolism, 75% had anaemia (haemoglobin < 10 g/dl) and 75% had a history of high oestrogen exposure (use of oestrogen-containing medications or pregnancy). In multivariable logistic regression analysis, anaemia remained significantly associated with thromboembolism (OR 5.60, 95% CI 1.55-24.30). CONCLUSIONS: Adenomyosis is associated with significantly higher prevalence of thromboembolism compared with endometriosis. Anaemia may further increase susceptibility, underscoring the importance of assessment of the risk of thromboembolism in women with adenomyosis.