Association between hormone replacement therapy and subsequent stroke: a meta-analysis

The cost-effectiveness of hormone therapy in younger and older postmenopausal women

PURPOSE

To evaluate the health and economic outcomes of hormone therapy in younger and older postmenopausal women.

METHODS

We developed a cost-effectiveness model to evaluate outcomes associated with hormone therapy in younger and older postmenopausal women, using data sources from published literature through March 2008. The target population was 50-year-old and 65-year-old women given hormone therapy or no therapy, and then followed over their lifetime. Primary outcomes measured were quality-adjusted life-years (QALYs) and incremental cost per QALY gained.

RESULTS

For the base-case analysis, hormone therapy for 15 years in the younger cohort resulted in a gain of 1.49 QALYs with an incremental cost of $2438 per QALY gained, compared with no therapy. The results for younger women were robust to all sensitivity analyses, and treatment remained highly cost-effective (<$10,000 per QALY gained) within the range of individual assumptions used. Treatment durations of 5 years and 30 years also were highly cost-effective. In the older cohort, treatment for 15 years resulted in a net gain of 0.11 QALYs with a cost of $27,953 per QALY gained. However, a loss of QALYs was seen in the first 9 years. The results for older women were sensitive to many of the assumptions used.

CONCLUSIONS

Hormone therapy for 5 to 30 years in younger postmenopausal women increases quality-adjusted life-years and is cost-effective. Hormone therapy started in later years results in a loss of quality-adjusted life for several years before a net gain can be realized.

Effect of raloxifene on stroke and venous thromboembolism according to subgroups in postmenopausal women at increased risk of coronary heart disease

BACKGROUND AND PURPOSE

Raloxifene, a selective estrogen receptor modulator, reduces risk of invasive breast cancer and osteoporosis, but the effect on risk for stroke and venous thromboembolism in different patient subgroups is not established. The purpose of this analysis was to evaluate the effect of raloxifene on the incidence of all strokes, stroke deaths, and venous thromboembolic events according to participant subgroups.

METHODS

This was a secondary end point analysis of an international, randomized, placebo-controlled clinical trial of 10 101 postmenopausal women with or at increased risk of coronary heart disease followed a median of 5.6 years. Strokes, venous thromboembolic events, and deaths were adjudicated by expert centralized committees. Strokes were categorized as ischemic, hemorrhagic, or undetermined and venous thromboembolic events were subclassified.

RESULTS

The incidences of all strokes did not differ between raloxifene (incidence rate per 100 woman-years=0.95) and placebo (incidence rate=0.86) treatment groups (P=0.30). In women assigned raloxifene versus placebo, there was a higher incidence of fatal strokes (incidence rates=0.22 and 0.15, respectively, P=0.0499) and venous thromboembolic events (incidence rates=0.39 and 0.27, respectively, P=0.02). No significant subgroup interactions were found except that there was a higher incidence of stroke associated with raloxifene use among current smokers.

CONCLUSIONS

In postmenopausal women at increased risk for coronary events, the incidences of venous thromboembolism and fatal stroke but not all strokes were higher in those assigned raloxifene versus placebo. Raloxifene's effect did not differ across subgroups, except that the risk of stroke differed by smoking status. Treatment decisions about raloxifene should be based on a balance of projected absolute risks and benefits.

Sex differences in stroke

Increasing evidence suggests that sex differences exist in the etiology, presentation, treatment, and outcome from stroke. The reasons for these sex disparities are becoming increasingly explored, but large gaps still exist in our knowledge. Experimental studies over the past several years have demonstrated intrinsic sex differences both in vivo and in animal models which may have relevance to our understanding of stroke in clinical populations. A greater understanding of the differences and similarities between males and females with respect to the risk factors, pathophysiology, and response to stroke will facilitate the design of future clinical trials and enhance the development of treatment strategies to improve stroke care in both sexes. This article reviews the current literature on sex differences in stroke with an emphasis on the clinical data, incorporating an analysis of bench research as it pertains to the bedside.

Could transdermal estradiol + progesterone be a safer postmenopausal HRT? A review

Hormone replacement therapy (HRT) in young postmenopausal women is a safe and effective tool to counteract climacteric symptoms and to prevent long-term degenerative diseases, such as osteoporotic fractures, cardiovascular disease, diabetes mellitus and possibly cognitive impairment. The different types of HRT offer to many extent comparable efficacies on symptoms control; however, the expert selection of specific compounds, doses or routes of administration can provide significant clinical advantages. This paper reviews the role of the non-oral route of administration of sex steroids in the clinical management of postmenopausal women. Non-orally administered estrogens, minimizing the hepatic induction of clotting factors and others proteins associated with the first-pass effect, are associated with potential advantages on the cardiovascular system. In particular, the risk of developing deep vein thrombosis or pulmonary thromboembolism is negligible in comparison to that associated with oral estrogens. In addition, recent indications suggest potential advantages for blood pressure control with non-oral estrogens. To the same extent, a growing literature suggests that the progestins used in association with estrogens may not be equivalent. Recent evidence indeed shows that natural progesterone displays a favorable action on the vessels and on the brain, while this might not be true for some synthetic progestins. Compelling indications also exist that differences might also be present for the risk of developing breast cancer, with recent trials indicating that the association of natural progesterone with estrogens confers less or even no risk of breast cancer as opposed to the use of other synthetic progestins. In conclusion, while all types of hormone replacement therapies are safe and effective and confer significant benefits in the long-term when initiated in young postmenopausal women, in specific clinical settings the choice of the transdermal route of administration of estrogens and the use of natural progesterone might offer significant benefits and added safety.

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.

Alzheimer's disease and other neurological disorders

Menopausal status and estrogen-containing hormone therapy may influence several neurological disorders, including Alzheimer's disease, epilepsy, migraine headache, multiple sclerosis, Parkinson's disease, sleep disorders, and stroke. For most of these illnesses, evidence on hormone therapy is insufficient to guide practice decisions. For stroke, clinical trial evidence indicates that hormone therapy increases risk of cerebral infarction. For women with Alzheimer's disease, estrogen treatment trials have tended to be small and of short duration. Most suggest that estrogen started after the onset of dementia symptoms does not meaningfully improve cognition or slow disease progression. Hormone therapy initiated after age 64 increased all-cause dementia in the Women's Health Initiative Memory Study. Many observational studies, however, report protective associations between hormone use and Alzheimer risk. Apparent risk reduction may represent a bias toward hormone therapy, since hormones are more often prescribed to healthier women. However, when compared to the Women's Health Initiative Memory Study, estrogen exposures in many observational studies reflect hormone initiation at a younger age, closer to the time of menopause. One intriguing hypothesis is that hormone therapy initiated or used during an early critical window may reduce later Alzheimer incidence. Public health implications of this hypothesis are important, but current data are inadequate to decide the issue.

Menopause and stroke and the effects of hormonal therapy

The incidence of stroke increases substantially after menopause, and in the United States it is the third leading cause of death. Data exist suggesting that women have worse outcomes for stroke than do men. Trials of aspirin use further suggest that there is a gender difference regarding stroke. While men may have a coronary benefit from aspirin, postmenopausal women do not; yet ischemic stroke may be decreased in women but not in men. Among the traditional risk factors for stroke (such as smoking, hypertension, diabetes, obesity), hormonal therapy (HT) has been suggested to be a risk as well, although the data are not consistent. The previous Position Statement of the IMS published in 2004 was relatively silent on the issue of stroke. The annual rate of stroke in women increases rapidly with aging in postmenopausal women. While the rate is approximately 0.6-0.8/1000/year at age 50-59, it is over 2/1000 after age 60. In white women in the USA, it is 4.2/1000 at 65-74 years of age, and 11.3/1000 between ages 75 and 84 years. Thus, in trials such as the Women's Health Initiative (WHI), most of the strokes occurred in older women. Both the conjugated equine estrogen/medroxyprogesterone acetate (CEE/MPA) and CEE-alone trials in the WHI reported an increased risk of stroke in the entire population using nominal statistics: 1.41 (95% confidence interval (CI) 1.07-1.85) and 1.39 (95% CI 1.10-1.77), respectively. The increased risk was related to ischemic stroke and not hemorrhagic stroke. The absolute risk for the entire population was 0.8/1000 and 1.2/1000 woman-years (<1/1000 signifies a 'rare' event using the CIOMS classification). However, the risk was not increased in the 50-59-year-old age group, although the numbers are small. Here, the background prevalence of stroke is much lower as noted above. The results of the observational trial of the WHI were not consistent with the randomized clinical trial data and were more in keeping with older observational data showing no increased risk of stroke. The authors reconcile these differences by suggesting differences in the timing of initiation of hormones, which was at an earlier age in the observational cohort. Several recent observational studies, which will be presented, show no increased risk of ischemic stroke in younger cohorts, but possibly an increase in the risk of transient ischemic attack. These recent studies suggested the risk to be less with lower doses of estradiol < or =1 mg and to be consistent with older studies showing no risk with doses < 0.625 mg CEE. In addition, the risk was possibly lower with non-oral therapy, and was reduced if started prior to menopause. The existence of hypertension was shown to substantially increase the risk. However, data on progestogen use versus unopposed estrogen have not been consistent. At the same time, a recent body of evidence from basic science studies has reaffirmed the neuronal and stroke protective effects of estrogen. Thus, the discrepancy between these data and clinical data showing no benefit or increased risk of stroke remains to be explained. Recent trials in older women with osteoporosis have suggested an increased risk of stroke with tibolone and of stroke mortality with raloxifene. In conclusion, the current data suggest no increased risk of stroke with hormone therapy in younger (50-59 years) normotensive postmenopausal women, particularly when lower doses are prescribed soon after menopause.

Improving depiction of benefits and harms: analyses of studies of well-known therapeutics and review of high-impact medical journals

The issues of weighing benefits and harms and of shared decision-making have become increasingly important in recent years. There is limited knowledge and lack of adequate data on the most transparent method of communicating the information. In this article we discuss examples of communicating benefits and harms for well-known therapeutics, illustrating that relative risk estimates are not helpful for communicating the chance of experiencing adverse events. In addition, we show that asymmetric presentation of the data for benefits and harms is likely to bias toward showing greater benefits and diminishing the importance of the harms (or vice versa). We also present preliminary results of a brief review of high-impact medical journals that show limitations of current systematic reviews. In the review we found that every second published study does not discuss frequency data and 1 in 3 studies that report information on both benefits and harms does not report information in the same metric. We conclude that consistently depicting benefit and harm information in frequencies can substantially improve the communication of benefits and harms. Investigators should be requested to provide frequency data along with relative risk information in the publication of their scientific findings. Currently, even in the highest impact medical journals, evidence of benefits and harms is not consistently presented in ways that facilitate accurate interpretation.

Hormone therapy and cerebrovascular events: a population-based nested case-control study

OBJECTIVE

The relationship between postmenopausal hormone therapy (HT) and cerebrovascular disease has been examined in several epidemiological studies and clinical trials with conflicting results. The authors aimed to evaluate the association between the use of HT and the incidence of first cerebrovascular event.

DESIGN

The study cohort comprised 158,031 women 50 to 69 years old registered in the U.K. General Practice Research Database between 1991 and 1997. The authors conducted a nested case-control analysis using all 920 confirmed cases of cerebrovascular events identified during the follow-up (536 of transient ischemic attack [TIA]; 259 of ischemic stroke; 125 of hemorrhagic stroke) and 10,000 controls.

RESULTS

The odds ratios of TIA, ischemic stroke, and hemorrhagic stroke among women currently using HT were 1.48 (95% CI, 1.17-1.87), 1.12 (95% CI, 0.78-1.59) and 1.21 (95% CI, 0.76-1.93), respectively, compared to never users. The overall risk estimate for having a cerebrovascular event was 1.34 (95% CI, 1.11-1.61). The risk of TIA was greater (1.96) among women using high doses of estrogen (95% CI, 1.34-2.87).

CONCLUSION

Overall, a small increased risk of stroke associated with HT use of comparable magnitude to the one observed in recent clinical trials was found. The increased risk was more apparent for TIA than for stroke and was greater at higher doses.

Traitement hormonal substitutif de la ménopause et risque vasculaire

Although experimental data and results of observational studies suggest that hormone replacement therapy (HRT) was associated with a reduction in the risk of heart disease, the results for stroke have been far less clear. Several recent randomized secondary prevention studies have found that HRT is not protective against the risk of coronary heart disease, stroke or progression of atherosclerosis. Moreover, an increased risk of stroke and first coronary event with hormone therapy has been found in low-risk healthy post menopausal women. In light of these findings, although the absolute risk of vascular event associated with HRT is low, most organizations recommend caution in using HRT. Hormone therapy should not be initiated to prevent vascular disease among postmenopausal women. There are numerous plausible explanations for the divergent findings from observational and randomized clinical trials of hormone therapy. Some discrepancies are certainly the result of methodological differences between the study designs. They also suggest other biological effects of hormone therapy than modification of classic vascular risk factors. Further studies should focus on identifying the mechanisms of risk and determining whether and how different regimens of hormone therapy influence vascular risk.

Prevention of Transient Ischemic Attack and Stroke in Older Adults: Implementing Evidence-Based Interventions

By the year 2030, it is estimated there will be more than 70 million adults age 55 and older. Despite the increased risk of transient ischemic attack and stroke after age 55, multiple evidence-based preventive actions can be taken to specifically target manageable health conditions and other modifiable factors that can substantially reduce their likelihood. The purpose of this article is to describe the essential elements in the transient ischemic attack and stroke risk assessment for older adults and the major evidence-based pharmacological and lifestyle stroke-prevention interventions for first ischemic strokes, transient ischemic attacks, and subsequent events.

Persistence with oral and transdermal hormone replacement therapy and hospitalisation for cardiovascular outcomes

BACKGROUND

The effect of persistence with transdermal and oral administrations of hormone replacement therapy (HRT) on the risk of hospitalisation for cardiovascular disease, and the role of income as potential confounder, were explored in a large population-based cohort study.

METHODS

Seventy-eight thousand eight hundred and seventy-five women resident in the Italian Lombardy Region aged 45-65 years who received at least one HRT prescription during 1998-2000 were followed until December 2003. The 828 cohort members who experienced at least one hospitalisation for a circulatory system disease were identified from the Regional hospital discharge database. The Regional prescription drug database was used to assess cumulative persistence with hormone treatment during follow-up. Data on individual taxable income was also obtained for women resident in the city of Milan. A proportional hazards model was fitted to estimate the association between cumulative time-dependent persistence with HRT and cardiovascular risk.

RESULTS

Compared with women who took HRT for less than 6 months, those exposed for more than 3 years to HRT as a whole, and to transdermal and oral HRT, respectively, showed hazard ratios of 0.65 (95% confidence interval: 0.45, 0.92), 0.53 (0.34, 0.82), and 1.15 (0.47, 2.79). CVD reducing potential of HRT disappeared when estimates were adjusted for income being hazard ratio associated with long-term use 0.94 (0.52, 1.71).

CONCLUSIONS

Evidence that CVD risk associated with long-term hormone treatment varies according to the route of HRT administration, and that economic position confounds the effect of HRT on the risk of cardiovascular hospitalisation, is provided by the current study.

Novel perspectives for progesterone in hormone replacement therapy, with special reference to the nervous system

The utility and safety of postmenopausal hormone replacement therapy has recently been put into question by large clinical trials. Their outcome has been extensively commented upon, but discussions have mainly been limited to the effects of estrogens. In fact, progestagens are generally only considered with respect to their usefulness in preventing estrogen stimulation of uterine hyperplasia and malignancy. In addition, various risks have been attributed to progestagens and their omission from hormone replacement therapy has been considered, but this may underestimate their potential benefits and therapeutic promises. A major reason for the controversial reputation of progestagens is that they are generally considered as a single class. Moreover, the term progesterone is often used as a generic one for the different types of both natural and synthetic progestagens. This is not appropriate because natural progesterone has properties very distinct from the synthetic progestins. Within the nervous system, the neuroprotective and promyelinating effects of progesterone are promising, not only for preventing but also for reversing age-dependent changes and dysfunctions. There is indeed strong evidence that the aging nervous system remains at least to some extent sensitive to these beneficial effects of progesterone. The actions of progesterone in peripheral target tissues including breast, blood vessels, and bones are less well understood, but there is evidence for the beneficial effects of progesterone. The variety of signaling mechanisms of progesterone offers exciting possibilities for the development of more selective, efficient, and safe progestagens. The recognition that progesterone is synthesized by neurons and glial cells requires a reevaluation of hormonal aging.

Nutrigenetics and nutraceuticals: the next wave riding on personalized medicine

The Human Genome Project and subsequent identification of single nucleotide polymorphisms (SNPs) within populations has played a major role in predicting individual response to drugs (pharmacogenetics) leading to the concept of "personalized medicine." Nutritional genomics is a recent off-shoot of this genetic revolution that includes (1) nutrigenomics: the study of interaction of dietary components with the genome and the resulting proteonomic and metabolomic changes; and (2) nutrigenetics: understanding the gene-based differences in response to dietary components and developing nutraceuticals that are most compatible with health based on individual genetic makeup. Despite the extensive data on genetic polymorphisms in humans, its translation into medical practice has been slow because of the time required to accumulate population data on SNP incidence, understand the significance of a given SNP in disease, and develop suitable diagnostic tests. Nutrigenomics revitalized the field by showing that nutrients and botanicals can interact with the genome and modify subsequent gene expression, which has provided a great impetus for nutrigenetic research and nutraceutical development based on nutrigenetics. Polymorphisms in methlyene tetrahydrofolate reductase (MTHFR) (involved in folate metabolism), apolipoprotein E (Apo E) and ApoA1 (in cardiovascular disease), and leptin/leptin receptor (obesity) genes are some good examples for understanding basic nutrigenetics. Developing nutraceuticals to prevent and manage thrombosis risk in women with thrombophilic gene mutations are discussed in the context of the opportunities that exist at the nutrigenetic/pharmacogenetic interphase leading to "personalized nutrition." Further research on individual differences in genetic profiles and nutrient requirements will help establish nutrigenetics as an essential discipline for nutrition and dietetics practice.

Hormone therapy and cardiovascular risk markers and disease: focus on progestagens

Biological studies have demonstrated estrogen's beneficial effect on cardiovascular risk factors, including plasma lipoproteins, atherogenesis, vascular reactivity, inflammation and antioxidative activity. Additionally, observational studies have supported a cardioprotective effect of hormone therapy (HT), although an underlying healthy-user effect may account for these observations. Progestagens are added to protect against an increased risk of endometrial cancer observed with unopposed estrogen treatment. The inclusion of progestagen in HT has been associated with possible adverse cardiovascular outcomes. Recent, large-scale, randomized clinical studies did not confirm a beneficial cardiovascular effect of HT. On the contrary, an increased risk was found with continuous combined estrogen-progestagen regimens. The progestagen used in these trials was medroxyprogesterone acetate and other progestagen components have only been sparsely elucidated. The purpose of the present review is to outline some of the modifying effects of different progestagens on the actions of estrogen on cardiovascular risk markers and clinical end points observed in biological, observational and clinical studies.

Tratamiento hormonal sustitutivo y enfermedades cardiovasculares

Despite biologically plausible mechanisms for cardiac protection and compelling evidence from observational studies suggesting that menopausal hormone therapy confers cardiovascular benefit, results of well-designed and conducted randomized clinical trials in healthy women and in women with established coronary heart disease displayed that menopausal hormone therapy failed to prevent clinical cardiovascular events and rather was associated with harms. Clinical trial of the SERM raloxifene also did not demonstrate a decrease in coronary events. It is unknown whether the earlier initiation of such therapies, i.e., at menopause, would result in favorable outcomes; or whether different hormonal preparations, lower doses, or alternate routes of administration would confer benefit. At present, proved coronary risk reduction strategies are requisite (albeit underutilized) for menopausal women; these include lifestyle and pharmacologic coronary preventive interventions. The baseline characteristics of menopausal women with coronary heart disease who were participants in cardiovascular outcome trials of menopausal hormone therapy or raloxifene were remarkably similar; globally, cardiovascular risk factors were not optimally controlled at entry into these trials, suggesting that more aggressive cardiovascular risk interventions are appropriate to achieve optimal target goals for menopausal women with documented coronary heart disease.

Postmenopausal osteoporosis and atheroma

Epidemiological studies have established a significant association between two major health problems, osteoporosis and atheroma, which is independent from age, gender, and other cardiovascular risk factors. Bone loss and the development of calcific deposits within vessel walls occur concomitantly. Proteins formerly thought to be specific of bone have been identified in atheroma lesions; and associations linking vertebral and proximal femoral fractures to aortic calcifications have been reported. Bone loss may be a marker for the risk of stroke and cardiovascular death. Bone loss may occur as a consequence of ischemia related to vascular disease. Despite numerous published studies, the mechanism underlying the osteoporosis-atheroma association remains controversial. Factors that perpetuate the debate include the often retrospective design of the studies, small sample sizes, and known limitations of absorptiometry as a tool for measuring osteoporosis severity. We reviewed the available clinical, epidemiological, and animal data on the mechanisms underlying the association between osteoporosis and atheroma. The possible effect of osteoporosis medications on the blood vessel wall is discussed. These issues remain a matter of debate, indicating a need for vast prospective studies to look for a causal link between osteoporosis and atheroma. The results of these studies may lead to new treatment strategies.

Estrogens and experimental ischemic stroke: a systematic review

Estrogens are believed to provide females with endogenous protection against cerebrovascular events although clinical trials studying long-term hormone replacement have yielded disappointing results. In contrast, estrogens might be neuroprotective after experimental ischemia. We performed a systematic review of controlled experimental studies that administered estrogens before, or after, cerebral ischemia and measured lesion volume. Relevant studies were found from searching PubMed, Embase and Web of Science. From 161 identified publications, 27 studies using 1,304 experimental subjects were analyzed using the Cochrane Review Manager software. Estrogens reduced lesion volume in a dose-dependent manner, after either transient (P<0.001) or permanent (P<0.001) ischemia and whether administered before or up to 4 h after ischemia onset; no studies assessed efficacy for later time periods. The effect size for estrogens decreased with increasing quality scores for studies of transient ischemia. Estrogens reduced lesion volume when administered to ovariectomized females and young adult males, but had no effect in intact females. Limited data were present for aged animals and the full dose-response relationship was not available in all experimental groups. On the basis of these data, estrogens are a candidate treatment for ischemic stroke, although further preclinical studies are also warranted.

Potential new risk factors for ischemic stroke: what is their potential?

BACKGROUND AND PURPOSE

About 60% to 80% of all ischemic strokes can be attributed to increasing blood pressure, blood cholesterol, cigarette smoking, carotid stenosis, and diabetes mellitus (atherosclerotic ischemic stroke), and atrial fibrillation and valvular heart disease (cardiogenic ischemic stroke). The aim of this review was to examine the potential role of other risk factors in the etiology of ischemic stroke.

SUMMARY OF REVIEW

About 10% to 20% of atherosclerotic ischemic strokes can probably be attributed to recently established, causal risk factors for ischemic heart disease: raised apoB/apoA 1 ratio, obesity, physical inactivity, pyschosocial stress and low fruit and vegetable intake. However, their causal role remains to be proven. The direct genetic contribution of any single gene towards ischemic stroke is likely to be modest and apply in selected patients only and in combination with environmental factors or via other epistatic (gene-gene or gene-environmental) effects.

CONCLUSIONS

Research resources should not be allocated disproportionately to emerging novel risk factors that may account for up to only 20% of all strokes at the expense of researching the determinants of the relatively few established causal factors that account for up to 80% of all strokes.

Estrogens as neuroprotectants against ischemic stroke

Estrogens have proven vasoprotective properties against atherosclerosis that depend on the direct effect on vascular smooth muscle and endothelium and on systemic actions that imply serum lipids, coagulation and fibrinolytic cascades, vasoactive proteins and antioxidant systems. They also have neuroprotective effects against cerebral ischemia that include antioxidant and anti-inflammatory effects, modulation of protein synthesis, inhibition of apoptosis and trophic effects and preservation of microvascular blood flow in the ischemic area. Estrogenic actions depend on activation of specific estrogen receptors that modulate gene expression and produce long-term effects on vascular endothelial and smooth muscle cells, neurons and glia, on interaction with plasma membrane sites that produce rapid non-genomic actions and also on receptor-independent mechanisms. This paper reviews what it is known about the mechanisms underlying the vaso- and neuroprotective effects of estrogens. Experimental and clinical evidences of such protective effects are also discussed. Therapeutical implications for stroke prevention and treatment derived from the available evidence are considered.

Hormone replacement therapy, brain volumes and white matter in postmenopausal women aged 60-64 years

Research on the structural and functional effects of hormone replacement therapy on the brain has produced inconsistent results. This paper reports on cross-sectional associations between hormone replacement therapy use and volumes of brain structures measured using magnetic resonance imaging in 213 postmenopausal women aged 60-64 years recruited from a large population study. Of these, 64 were current hormone replacement therapy users, 69 previous users and 80 had never used hormone replacement therapy. No differences were observed between groups in total grey matter, white matter, hippocampal or amygdalar volumes, severity or volume of white matter hyperintensities, or in different measures of brain atrophy. While acknowledging the limitations of a cross-sectional study, the results argue against hormone replacement therapy being protective against brain changes associated with ageing in women in their early 60s.

Systematic review: Hormone therapy and cardiovascular disease: a systematic review and meta-analysis

BACKGROUND

Despite decades of evidence from observational studies, the use of hormone therapy for the prevention of cardiovascular disease (CVD) among postmenopausal women is controversial. The recent completion of several randomised clinical trials examining the effects of hormone therapy on CVD presents an opportunity to provide a more precise estimate of the cardiovascular risks of hormone therapy.

OBJECTIVE

To summarise the effects of hormone therapy on CVD in postmenopausal women.

SEARCH STRATEGY

MEDLINE, EMBASE, the Cochrane Library, DARE and CENTRAL were searched for clinical trials reporting mortality and/or CVD outcomes in association with hormone therapy. Bibliographies and editorials were also reviewed. All studies were reviewed and rated for quality independently by two reviewers.

SELECTION CRITERIA

High quality, randomised placebo-controlled clinical trials of hormone therapy (duration greater than one year) in non-hospitalised postmenopausal women were included.

DATA COLLECTION AND ANALYSIS

Summary relative risks were estimated for all-cause mortality, coronary heart disease (CHD) mortality, non-fatal acute myocardial infarction (AMI) and all stroke.

MAIN RESULTS

Seven randomised clinical trials met the inclusion criteria. The use of hormone therapy had no significant effect on all-cause mortality, non-fatal AMI or CHD mortality, with relative risks of 1.02 [95% confidence interval (CI) 0.93-1.13], 1.00 (0.88-1.14) and 0.99 (0.82-1.21), respectively. For all stroke, the summary relative risk was 1.29 (1.13-1.48).

AUTHOR'S CONCLUSIONS

This systematic review, incorporating the latest available trial data, shows that hormone therapy does not significantly change the risk of all-cause morality, CHD death or non-fatal AMI but increases the risk of stroke in postmenopausal women.

Natural menopause and risk of stroke in elderly women

Although early natural menopause has been postulated to increase stroke risk, studies have not produced convincing results. We examined the associations between stroke risks and age at natural menopause or time since natural menopause. 5,731 naturally postmenopausal women more than 65 yr of age were followed from 1993 to 1998. Information on age at menopause and risk factors were obtained using mailed questionnaires. 186 cases of stroke occurred over a total 27,936 person-years. After adjusting for age, hypertension, and physical activity, age at menopause was not found to be significantly associated with stroke or cerebral infarction. However, adjusted relative risks (aRRs) showed a significant increasing tendency of hemorrhagic stroke versus age at menopause (aRRs, 0.66, 0.48, 1.00 and 2.33 for the following age groups at menopause; 40-44, 45-49, 50-54 [reference group], and > or =55 yr). Time since menopause (11-20, 21-30, and > or =31 yr) was not found to be significantly associated with cerebral infarction, or hemorrhagic stroke. Late menopause (menopause age > or =55 yr) showed a tendency of a lower risk of cerebral infarction (aRR, 0.79) and a higher risk of hemorrhagic stroke (aRR, 2.33). Further study is warranted to determine stroke risk in women during the decade following menopause.

Estradiol increases brain lesions in the cortex and lateral striatum after transient occlusion of the middle cerebral artery in rats: no effect of ischemia on galanin in the stroke area but decreased levels in the hippocampus

A distinctive feature of galanin expression is that it is extensively increased by neuronal injury, estrogens, Alzheimer's disease and during development. Since stroke is amongst the clinically most important causes of neuronal injury we studied the tissue concentrations of galanin in a rat stroke model and the possibility of modulating this effect with estrogen. Transient focal middle cerebral artery ischemia was induced in rats that 2 weeks earlier underwent ovariectomy and received 1.5mg 17beta-estradiol slow-release or placebo pellets. The concentrations of galanin and neuropeptide Y were measured after observation periods of 3, 7 and 14 days in extracts of punch biopsies from both the lesioned and the contra lateral control hemisphere. The galanin levels were not changed in any of the brain regions studied except in the hippocampus where they were lower in the ischemic hemisphere in both the estrogen- and placebo-treated animals compared to the corresponding contra lateral intact hemisphere (p=0.015). Estrogen treatment up-regulated galanin concentrations in both the ventral and dorsal hippocampus (p=0.003). The effects on the galanin concentrations were similar after all observation periods: 3, 7 and 14 days (p=0.144). No significant changes were observed in the concentration of neuropeptide Y in response to the lesions. The ischemic lesions were markedly larger in the estrogen-treated animals observed after 3 days compared to the corresponding control group. In the estrogen group the lesion was largest at bregma and the slice 2mm anterior to the bregma, 82% and 435% larger than in the control group (p<0.001). A similar, but much less pronounced (not statistically significant) difference was seen in the groups observed after 7 and 14 days. Earlier studies of lesions in the peripheral and central nervous systems have generally shown an up-regulation of galanin markers in response to but at a distance from the injury. Our results indicate that galanin is not involved in the response of the ischemic penumbra itself to stroke, whereas it may participate in the reactions of the neural stem-cell rich hippocampus to stroke.

Neuroprotection and protein damage prevention by estradiol replacement in rat hippocampal slices exposed to oxygen-glucose deprivation

Here we investigated the effects of estradiol replacement in ovariectomized female rats using hippocampal slices exposed to oxygen-glucose deprivation (OGD). OGD induced lactate dehydrogenase (LDH) release to the incubation medium, what was assumed as a parameter of cellular death. In the estradiol-treated group the LDH release was markedly decreased by 23% as compared to the vehicle-treated group. In attempt to study a possible mechanism by which estradiol acts, we investigated some parameters of oxidative stress. In both vehicle-treated and estradiol-treated groups, OGD significantly increased the free radical production by 34% and 16%, respectively, although no significant differences on total antioxidant capacity were observed. Interestingly, estradiol replacement prevented the significant reduction in tryptophan and tyrosine contents caused by OGD observed in vehicle-treated animals. Our results show that estradiol replacement in ovariectomized female rats decreases cellular susceptibility to an ischemic-like injury and suggest a role for the hormone on protein damage prevention.