Esterified estrogen and conjugated equine estrogen and the risk of incident myocardial infarction and stroke

Background: Clinical trials of conjugated equine estrogen (CEE) or estradiol vs placebo in postmenopausal women have found no effect or an elevated risk of myocardial infarction (MI) and stroke. The association of these end points with the use of esterified estrogen (EE) is unknown. Methods: We examined the risk of MI and stroke associated with current use of CEE, use of EE, or nonuse of hormones in a population-based case-control study in a health maintenance organization. Cases were all postmenopausal women with an incident MI ( n= 1644) or stroke ( n= 1080). Controls ( n= 4205) consisted of a random sample of postmenopausal women without MI or stroke. Current use of postmenopausal hormones was assessed using a computerized pharmacy database. Results: There was no difference in risk of MI or stroke associated with current use of CEE or EE compared with nonuse or for current use of CEE compared with EE. In analyses restricted to hormone users, there was a suggestion of higher ischemic stroke risk associated with CEE alone ( without progestin) compared with EE alone ( odds ratio, 1.57; 95% confidence interval, 0.98-2.53). There was also a suggestion that when initiated in the previous 6 months, CEE was associated with a higher risk of MI than EE ( odds ratio, 2.33; 95% confidence interval, 0.93-5.82). Conclusion: Further study may be warranted of the effects of EE on the risk of cardiovascular end points.