Hormone replacement therapy and acute myocardial infarction: a large observational study exploring the influence of age

Risk patterns in drug safety study using relative times by accelerated failure time models when proportional hazards assumption is questionable: an illustrative case study of cancer risk of patients on glucose-lowering therapies

Observational drug safety studies may be susceptible to confounding or protopathic bias. This bias may cause a spurious relationship between drug exposure and adverse side effect when none exists and may lead to unwarranted safety alerts. The spurious relationship may manifest itself through substantially different risk levels between exposure groups at the start of follow-up when exposure is deemed too short to have any plausible biological effect of the drug. The restrictive proportional hazards assumption with its arbitrary choice of baseline hazard function renders the commonly used Cox proportional hazards model of limited use for revealing such potential bias. We demonstrate a fully parametric approach using accelerated failure time models with an illustrative safety study of glucose-lowering therapies and show that its results are comparable against other methods that allow time-varying exposure effects. Our approach includes a wide variety of models that are based on the flexible generalized gamma distribution and allows direct comparisons of estimated hazard functions following different exposure-specific distributions of survival times. This approach lends itself to two alternative metrics, namely relative times and difference in times to event, allowing physicians more ways to communicate patient's prognosis without invoking the concept of risks, which some may find hard to grasp. In our illustrative case study, substantial differences in cancer risks at drug initiation followed by a gradual reduction towards null were found. This evidence is compatible with the presence of protopathic bias, in which undiagnosed symptoms of cancer lead to switches in diabetes medication.

Postmenopausal hormone therapy and coronary heart disease in early postmenopausal women

In women, cardiovascular disease (CVD) accounts for about half of all deaths in Western countries. It is generally accepted that endogenous estrogen protects premenopausal women from CVD. However, whether postmenopausal hormone therapy (HT) confers cardiovascular benefit or harm remains controversial. One of the most pronounced factors modifying the cardiovascular effects of HT is age or time since menopause at the initiation of HT. Recently also the impact of hot flushes on CVD risk and the outcomes of HT has gained attention. This review summarizes the newest data regarding HT and CVD in recently postmenopausal women aged 50-59 years in light of the results from older HT trials. The aim is to help clinicians counsel their patients regarding the individual risks and benefits associated with HT use in this age group, where HT use is most prevalent.

Meta-analyses of adverse effects data derived from randomised controlled trials as compared to observational studies: methodological overview

BACKGROUND

There is considerable debate as to the relative merits of using randomised controlled trial (RCT) data as opposed to observational data in systematic reviews of adverse effects. This meta-analysis of meta-analyses aimed to assess the level of agreement or disagreement in the estimates of harm derived from meta-analysis of RCTs as compared to meta-analysis of observational studies.

METHODS AND FINDINGS

Searches were carried out in ten databases in addition to reference checking, contacting experts, citation searches, and hand-searching key journals, conference proceedings, and Web sites. Studies were included where a pooled relative measure of an adverse effect (odds ratio or risk ratio) from RCTs could be directly compared, using the ratio of odds ratios, with the pooled estimate for the same adverse effect arising from observational studies. Nineteen studies, yielding 58 meta-analyses, were identified for inclusion. The pooled ratio of odds ratios of RCTs compared to observational studies was estimated to be 1.03 (95% confidence interval 0.93-1.15). There was less discrepancy with larger studies. The symmetric funnel plot suggests that there is no consistent difference between risk estimates from meta-analysis of RCT data and those from meta-analysis of observational studies. In almost all instances, the estimates of harm from meta-analyses of the different study designs had 95% confidence intervals that overlapped (54/58, 93%). In terms of statistical significance, in nearly two-thirds (37/58, 64%), the results agreed (both studies showing a significant increase or significant decrease or both showing no significant difference). In only one meta-analysis about one adverse effect was there opposing statistical significance.

CONCLUSIONS

Empirical evidence from this overview indicates that there is no difference on average in the risk estimate of adverse effects of an intervention derived from meta-analyses of RCTs and meta-analyses of observational studies. This suggests that systematic reviews of adverse effects should not be restricted to specific study types. Please see later in the article for the Editors' Summary.

Association between hormone replacement therapy and subsequent arterial and venous vascular events: a meta-analysis

AIMS

Randomized controlled trials (RCTs) have shown that the risk of stroke and venous thromboembolism (VTE) is increased with hormone replacement therapy (HRT); the effect on coronary heart disease (CHD) remains unclear.

METHODS AND RESULTS

RCTs of HRT were identified. Event rates for cerebrovascular disease [stroke, TIA (transient ischaemic attack)], CHD (myocardial infarction, unstable angina, sudden cardiac death), and VTE (pulmonary embolism, deep vein thrombosis) were analysed. Sensitivity analyses were performed by type of HRT (mono vs. dual) and subject age. 31 trials (44 113 subjects) were identified. HRT was associated with increases in stroke (odds ratio, OR, 1.32, 95% confidence intervals, CI, 1.14-1.53) and VTE (OR 2.05, 95% CI 1.44-2.92). In contrast, CHD events were not increased (OR 1.02, 95% CI 0.90-1.11). Ordinal analyses confirmed that stroke severity was increased with HRT (OR 1.31, 95% CI 1.12-1.54). Although most trials included older subjects, age did not significantly affect risk. The addition of progesterone to oestrogen doubled the risk of VTE.

CONCLUSION

HRT is associated with an increased risk of stroke, stroke severity, and VTE, but not of CHD events. Although most trials studied older patients, increased risk was not related to age. Combined HRT increases the risk of VTE compared with oestrogen monotherapy.

A simulation using data from a primary care practice database closely replicated the women's health initiative trial

OBJECTIVE

In contrast to prior observational studies, hormone replacement therapy (HRT) did not prevent coronary heart disease in the Women's Health Initiative Randomized Controlled Trial (WHI RCT). To assess the validity of a novel observational study design, we compared the WHI RCT with a simulation using data from the United Kingdom General Practice Research Database (GPRD).

STUDY DESIGN AND SETTING

A cohort from GPRD was used to simulate the WHI RCT by replicating, to the extent possible, all aspects of the RCT except randomization. The study included 37,730 Unexposed and 13,658 Exposed women treated with estrogen and norgestrel.

RESULTS

Myocardial infarction (adjusted hazard ratio 0.95 [0.78-1.16]) was not decreased significantly in the GPRD Exposed group. Similar to the WHI RCT, stroke, venous thromboembolic events, and breast cancer were increased; and colorectal cancer was decreased. Although death appeared to decrease in the total cohort, it was unaltered in a subset of subjects without missing data on baseline covariates.

CONCLUSION

A structured comparison using data from GPRD was largely concordant with the WHI RCT and did not show a cardioprotective effect of HRT. These findings further generalize the results of WHI and reinforce the potential utility of this analytic approach.

Cardiovascular risk and hormone replacement therapy

PURPOSE OF REVIEW

The purpose of this review is to summarize the studies in humans of the relationship between hormone replacement therapy and coronary heart disease and stroke.

RECENT FINDINGS

Randomized controlled trial evidence of the effect of hormone replacement therapy on coronary heart disease, stroke and atherosclerosis comes from nine individual secondary prevention randomized controlled trials, four individual primary prevention randomized controlled trials and a pooled analysis of 22 randomized controlled trials that had primary aims to examine noncardiovascular outcomes but which reported cardiovascular events by randomized groups. With the exception of one small primary prevention randomized controlled trial that found a weak protective effect of hormone replacement therapy on the progression of carotid artery intima media thickness, all other randomized controlled trials have found hormone replacement therapy either increases the risk of cardiovascular disease or has no effect.

SUMMARY

Randomized controlled trial evidence conducted in a variety of populations suggests that hormone replacement therapy is not protective against the risk of coronary heart disease, stroke or progression of atherosclerosis. The prevention of cardiovascular disease in women, as in men, should focus on implementing effective methods of reducing smoking, obesity, high blood pressure, dyslipidaemia and glucose intolerance.