Does hormone therapy exacerbate other venous thromboembolism risk factors?

Objective: Postmenopausal symptoms in women at higher risk for venous thromboembolism (VTE) due to comorbidities are often undertreated because of concerns that hormone therapy (HT) may increase VTE risk; however, it is unclear how much HT impacts risk of VTE when compared with other risk factors. Methods: This is a case-control study in a commercial claims database from 2007 to 2019. Women aged 50 to 64 years (n = 223,949) were classified as cases if they had an International Classification of Diseases code indicating an acute VTE plus a filled prescription for an anticoagulant, placement of intravascular vena cava filter, or death within 30 days of diagnosis. Controls were matched 10:1 to each case by index date and age. Risk factors and comorbidities present within the year before index were examined. Exposure was defined as a HT prescription within 60 days before index. Results: There were 20,359 VTE cases and 203,590 matched controls. A conditional logistic regression indicated that the greatest risks for VTE were from metastatic cancer (odds ratio [OR], 13.66; 95% CI, 12.64-14.75), hospitalization/surgery (OR, 8.51; 95% CI, 8.09-8.96), trauma (OR, 3.52; 95% CI, 3.32-3.73), comorbidity burden (OR, 3.51; 95% CI, 3.34-3.69), history of hypercoagulable condition (OR, 3.10; 95% CI, 2.87-3.36), and varicose veins (OR, 2.87; 95% CI, 2.56-3.22). Regarding hormone exposure, we observed ORs of 1.51 (95% CI, 1.43-1.60) for any recent hormone exposure; 1.13 (95% CI, 1.04-1.23; number needed to harm, 4,274) for unopposed estrogen menopausal HT; 1.23 (95% CI, 1.10-1.38; number needed to harm, 2,440) for combined menopausal HT; and 5.22 (95% CI, 4.67-5.84) for combined hormonal contraceptives compared with no recent HT exposure. Conclusions: Hormone therapy exposure did not appear to adversely influence other risk factors, and exposure generally played a minor role in VTE risk. Contraceptives, however, were a strong risk factor.