Vinogradova Y, Coupland C, Hippisley-Cox J. Use of hormone replacement therapy and risk of venous thromboembolism: nested case-control studies using the QResearch and CPRD databases. BMJ. 2019;364:k4810.
The Women’s Health Initiative trials, in which menopausal women were randomly assigned to treatment with oral CEE or placebo, found that statistically the largest risk associated with menopausal hormone therapy (HT) was increased VTE.1 Recently, investigators in the United Kingdom (UK) published results of their research aimed at determining the association between the risk of VTE and the use of different types of HT.2
Details of the study
Vinogradova and colleagues used 2 UK primary care research databases, QResearch and Clinical Practice Research Datalink, to identify cases of incident VTE in general practice records, hospital admissions, and mortality records. They identified 80,396 women (aged 40 to 79 years) diagnosed with VTE between 1998 and 2017 and 391,494 control women matched by age and general practice. The mean age of the case and control women was approximately 64 years; the great majority of women were white. Analyses were adjusted for smoking, body mass index (BMI), family history of VTE, and comorbidities associated with VTE.
Types of HT used. The investigators found that 5,795 (7.2%) women with VTE and 21,670 (5.5%) controls were exposed to HT in the 90 days before the index date (the first date of VTE diagnosis for cases became the index date for matched controls). In those exposed to HT:
- 4,915 (85%) cases and 16,938 (78%) controls used oral preparations (including 102 [1.8%] cases and 312 [1.4%] controls who also had transdermal preparations)
- 880 (14%) cases and 4,731 (19%) controls used transdermal HT only.
Association of VTE with HT. Risk of VTE was increased with all oral HT formulations, including combined (estrogen plus progestogen) and estrogen-only preparations. Use of oral CEE (odds ratio [OR], 1.49) and estradiol (OR, 1.27) were both associated with an elevated risk of VTE (P<.05 for both comparisons). In contrast, use of transdermal estradiol (the great majority of which was administered by patch) was not associated with an elevated risk of VTE (OR, 0.96).
Direct comparison of oral estradiol and CEE found that the lower VTE risk with oral estradiol achieved statistical significance (P = .005). Direct comparison of oral and transdermal estrogen revealed an OR of 1.7 for the oral route of administration (P<.001)
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