- Analysis of 2 nested case-control studies suggests that oral hormone replacement therapy (HRT) is associated with increased risk for venous thromboembolism (VTE), whereas transdermal HRT is not.
Why this matters
- This study suggests that despite the greater popularity of oral HRT formulations, transdermal formulations are safer in terms of VTE risk.
- Overall exposure to HRT was associated with increased VTE risk (aOR, 1.43; 95% CI, 1.38-1.48) compared with no exposure.
- Oral HRT was associated with increased VTE risk (aOR, 1.58; 95% CI, 1.52-1.64) compared with no exposure.
- aOR, 1.40 (95% CI, 1.32-1.48) for estrogen-only preparations.
- aOR, 1.73 (95% CI, 1.65-1.81) for combined preparations.
- Estradiol had lower VTE risk compared with conjugated equine estrogen for estrogen-only preparations (aOR, 0.85; 95% CI, 0.76-0.95) and combined preparations (aOR, 0.83; 95% CI, 0.76-0.91).
- Transdermal HRT was not associated with increased VTE risk (aOR, 0.93; 95% CI, 0.87-1.01) compared with no exposure.
- 80,396 women aged 40-79 years who experienced VTE and 391,494 matched control patients were analyzed.
- 5795 women who experienced VTE and 21,670 women who did not experience VTE had been exposed to HRT within 90 days before the index date.
- Funding: None.
- Observational study.