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A Systematic Review to Update the U.S. Preventive Services Task Force Recommendations
Release Date: May 2012
By Heidi D. Nelson, MD, MPH; Miranda Walker, MA; Bernadette Zakher, MBBS; and Jennifer Mitchell, BA.
The information in this article is intended to help clinicians, employers, policymakers, and others make informed decisions about the provision of health care services. This article is intended as a reference and not as a substitute for clinical judgment.
This article may be used, in whole or in part, as the basis for the development of clinical practice guidelines and other quality enhancement tools, or as a basis for reimbursement and coverage policies. AHRQ or U.S. Department of Health and Human Services endorsement of such derivative products may not be stated or implied.
This article was first published in Annals of Internal Medicine on May 29, 2012 (Ann Intern Med 2012;157:1-10; http://www.annals.org).
Background: Menopausal hormone therapy to prevent chronic conditions is currently not recommended because of its adverse effects.
Purpose: To update evidence about the effectiveness of hormone therapy in reducing risk for chronic conditions and adverse effects, and to examine whether outcomes vary among women in different subgroups.
Data Sources: MEDLINE (January 2002 to November 2011), Cochrane Central Register of Controlled Trials and Cochrane Database of Systematic Reviews (through the 3rd quarter of 2011), Scopus, and reference lists.
Study Selection: Randomized, placebo-controlled trials of menopausal hormone therapy published in English since 2002 that assessed primary prevention of chronic conditions.
Data Extraction: Investigators extracted data on participants, study design, analysis, follow-up, and results; 2 investigators independently rated study quality by using established criteria.
Data Synthesis: 9 fair-quality trials met the inclusion criteria. The Women's Health Initiative reported most of the results, had 11 years of follow-up, and had data most applicable to postmenopausal women in the United States. It showed that estrogen plus progestin reduced fractures (46 fewer per 10,000 woman-years) and increased invasive breast cancer (8 more per 10,000 woman-years), stroke (9 more per 10,000 woman-years), deep venous thrombosis (12 more per 10,000 woman-years), pulmonary embolism (9 more per 10,000 woman-years), lung cancer death (5 more per 10,000 woman-years), gallbladder disease (20 more per 10,000 woman-years), dementia (22 more per 10,000 woman-years), and urinary incontinence (872 more per 10,000 woman-years). Estrogen-only therapy reduced fractures (56 fewer per 10,000 woman-years) and invasive breast cancer incidence (8 fewer per 10,000 woman-years) and death (2 fewer per 10,000 woman-years) and increased stroke (11 more per 10,000 woman-years), deep venous thrombosis (7 more per 10,000 woman-years), gallbladder disease (33 more per 10,000 woman-years), and urinary incontinence (1271 more per 10,000 woman-years). Outcomes did not consistently differ by age or comorbid conditions.
Limitation: Limitations of the trials included low adherence, high attrition, inadequate power to detect risks for some outcomes, and evaluation of few regimens.
Conclusion: Estrogen plus progestin and estrogen alone decreased risk for fractures but increased risk for stroke, thromboembolic events, gallbladder disease, and urinary incontinence. Estrogen plus progestin increased risk for breast cancer and probable dementia, whereas estrogen alone decreased risk for breast cancer.
Primary Funding Source: Agency for Healthcare Research and Quality.
Menopausal hormone therapy includes various forms, doses, and regimens of estrogen, alone or combined with progestin (1). The combined regimen is used by a woman with a uterus to prevent endometrial proliferation and endometrial cancer (1). Before the WHI (Women's Health Initiative) trials (2, 3), menopausal hormone therapy was routinely used by postmenopausal women to prevent chronic conditions, such as cardiovascular disease, dementia, and osteoporosis. However, the initial results of the trials, published for estrogen plus progestin in 2002 (2, 3) and for estrogen only in 2004 (2, 3), indicated important adverse health effects. In response, the U.S. Preventive Services Task Force (USPSTF) issued recommendations against using hormone therapy to prevent chronic conditions for estrogen plus progestin in 2002 (4) and for estrogen only in 2005 (5). Several other professional groups provided similar recommendations (6–10). The current indications for use from the U.S. Food and Drug Administration include short-term treatment of menopausal symptoms, such as vasomotor hot flashes or urogenital atrophy, and prevention of osteoporosis (1).
Our systematic review for the USPSTF updates evidence about the effectiveness of hormone therapy in reducing risks for chronic conditions and its adverse effects, and examines differences in outcomes among population subgroups. Use of hormone therapy to treat menopausal symptoms or for other indications is outside its scope. This update focuses on studies published since 2002 and evidence gaps that were unresolved at the time of the previous recommendations.
Key Questions and Analytic Framework
We developed and followed a standard protocol. A technical report (11) details the methods and includes search strategies and additional evidence tables. Key questions were based on evidence from the previous review (12) and developed by using the methods of the USPSTF (13) to address the benefits and harms of menopausal hormone therapy to prevent chronic conditions and differences between population subgroups. Subgroups are defined by premature menopause; surgical menopause; age; type, dose, and method of hormone delivery; and presence of comorbid conditions. Investigators created an analytic framework incorporating the key questions and outlining the patient populations, interventions, outcomes, and harms (Appendix Figure 1).
The target population includes postmenopausal adult women eligible for hormone therapy. Women with known contraindications, such as thrombotic disorders or hormone-sensitive cancer (1), would be ineligible and are outside the scope of this review. Outcomes include cardiovascular disease, such as coronary heart disease (CHD), stroke, and thromboembolic disease (deep venous thrombosis [DVT] and pulmonary embolism [PE]); cancer of the breast, colon, lung, endometrium, or ovaries; fractures at various sites; cognition and dementia; disease-specific and all-cause mortality; and new findings reported by the trials. This review includes health outcomes (such as fractures) rather than intermediate outcomes (such as bone mineral density) and emphasizes medications, health care settings, and populations of postmenopausal women applicable to U.S. primary care practice.
Data Sources and Searches
In conjunction with a research librarian, we searched the Cochrane Central Register of Controlled Trials and Cochrane Database of Systematic Reviews (through the 3rd quarter of 2011), MEDLINE (2002 to 30 November 2011), reference lists of papers, and Scopus for relevant English-language studies and systematic reviews.
We selected studies on the basis of inclusion and exclusion criteria developed for each key question. For all key questions, we included only randomized, controlled trials of postmenopausal hormone therapy versus placebo. We did not include observational studies because of the existence of published randomized trials designed to address the key questions directly and the known biases inherent in observational studies of menopausal hormone use. We included trials that matched the target population, evaluated the primary prevention of new conditions rather than treatment of existing conditions, and provided risk reduction or elevation estimates for hormone therapy compared with placebo. We included estimates for individual hormone therapy regimens and excluded estimates that pooled results from different regimens. For trials that enrolled women with preexisting conditions, such as CHD in HERS (Heart and Estrogen/progestin Replacement Study), we used data for all outcomes except preexisting conditions and related conditions.
For trials that reported outcomes at various times, we selected results appropriate to specific outcome measures. For conditions known to be related to ongoing exposure to hormone therapy, such as thromboembolic disease and osteoporotic fractures, we selected results reported at the end of the trial intervention phase. For conditions that were initiated during exposure but continued after the intervention phase, such as cancer, we used results reported at the end of the trial's postintervention phase, if available. We reviewed our selection of results from the WHI trials with the WHI investigators.
Data Extraction and Quality Assessment
From the included studies, an investigator abstracted details of the patient population, study design, analysis, follow-up, and results. Key data elements were confirmed by a second investigator. By using predefined criteria developed by the USPSTF for randomized trials (13), 2 investigators independently rated the quality of studies (good, fair, or poor) and resolved discrepancies by consensus.
Data Synthesis and Analysis
We used results from the WHI trials, including the main trials, WHIMS (Women's Health Initiative Memory Study), and WHISCA (Women's Health Initiative Study of Cognitive Aging), as the main estimates for each outcome rather than perform meta-analysis of all trials because the trials were heterogeneous, the WHI trials were most applicable to the key questions, and the results from these trials would dominate the meta-analysis because of their large enrollment. As a group, the research team used methods developed by the USPSTF to assess the overall quality of the body of evidence for each key question (good, fair, or poor) on the basis of the number, quality, and size of studies; consistency of results between studies; and directness of evidence (13).
The draft report was reviewed by content experts, USPSTF members, the Agency for Healthcare Research and Quality (AHRQ) program officers, and collaborative partners.
Role of the Funding Source
AHRQ funded this research under a contract to support the work of the USPSTF. Researchers worked with USPSTF members and AHRQ staff to define the scope, analytic framework, and key questions; resolve issues arising during the project; and review the final report to ensure that it met basic methodological standards for systematic reviews. AHRQ provided project oversight, reviewed the draft report, and distributed the draft for external review by outside experts. AHRQ had no role in the selection, critical appraisal, or synthesis of evidence. The investigators were solely responsible for the content and the decision to submit the manuscript for publication.
Of 4524 abstracts identified from searches, 51 full-text articles from 9 trials (2, 3, 14–62) met our inclusion criteria (Appendix Figure 2). We also included an article with new results from the WHI (63), which was published after our literature search.
Characteristics of Included Trials
The 9 placebo-controlled trials were the 2 main WHI trials (2, 3, 14–40, 63), WHIMS (41–45), WHISCA (46–48), EMS (Estrogen Memory Study) (49), HERS (50–56), ESPRIT (Oestrogen in the Prevention of Reinfarction Trial) (57), ULTRA (Ultra–Low-Dose Transdermal Estrogen Assessment) (58–61), and WISDOM (Women's International Study of Long-Duration Oestrogen After Menopause) (62) (Appendix Table).
The main WHI trials compared conjugated equine estrogen (CEE), 0.625 mg/d, plus medroxyprogesterone acetate (MPA), 2.5 mg/d, with placebo (64) or CEE only with placebo (2) in women with hysterectomies. The trials recruited women aged 50 to 79 years at several sites in the United States, enrolling 16,608 in the estrogen plus progestin trial and 10,739 in the estrogen-only trial. The primary outcome was CHD, and the primary adverse event outcome was invasive breast cancer. Secondary outcomes included fracture incidence at the hip and other sites; stroke; thromboembolism; endometrial, colorectal, and other types of cancer; and mortality. A global index of risks and benefits, including the primary outcomes as well as stroke, PE, colorectal cancer, hip fracture, and death from other causes, was used to summarize overall effects.
The data and safety monitoring boards stopped both trials early because of increased adverse effects of hormone therapy. Although planned for 8.5 years, the estrogen plus progestin trial was stopped in 2002 after an average of 5.2 years because the increases in breast cancer, CHD, stroke, and PE outweighed the reductions in fractures and colon cancer (3). After participants stopped receiving medication, follow-up assessments of outcomes continued until the end of the predefined trial period in 2005 (28); 95% of participants were followed for a postintervention period of 2.5 years (18) and 83% for a further extension period until 2009 (18), for a cumulative follow-up of 11 years. The estrogen-only trial was terminated in 2004 because of an increased risk for stroke in the estrogen group after an average follow-up of 6.8 years. Approximately 78% of participants agreed to continue follow-up for a total of 10.7 years (18, 34).
The WHI was not a head-to-head trial of estrogen plus progestin versus estrogen only. Moreover, the characteristics of women enrolled in the 2 main WHI trials differed (Table 1) (2, 3). Women in the estrogen-only trial had more risk factors for cardiovascular disease, including higher body mass index (BMI); history of myocardial infarctions, stroke, and thromboembolism; higher systolic and diastolic blood pressure; and treatment for elevated cholesterol levels, hypertension, and diabetes. Women in the estrogen-only trial had fewer risk factors for breast cancer, including previous hysterectomy and bilateral oophorectomy, lower rates of nulliparity, and a smaller proportion of women who first became pregnant at age 30 years or older. More women in the estrogen-only trial had relatives with breast cancer and higher BMI, both of which increase risk for breast cancer.
Three trials were designed for cognitive outcomes, including the WHIMS and WHISCA trials of women enrolled in the main WHI trials. WHIMS (45) evaluated the effect of hormone therapy on probable dementia in women aged 65 years or older with normal cognition by using the Modified Mini-Mental State Examination. Secondary outcomes were mild cognitive impairment and global cognitive function. WHISCA (47, 48) enrolled women from 14 of the 39 WHIMS sites to evaluate cognitive function by using a battery of tests. The EMS (49) is a small trial of a cyclic regimen of 17-β estradiol plus norethindrone versus placebo that reported measures of memory (short-delay verbal recall, immediate recall, new list recall, cued recall, and recognition memory).
Two secondary prevention trials evaluated the effect of hormone therapy on CHD events and several additional outcomes. HERS, which compared CEE plus MPA with placebo, enrolled 2763 postmenopausal women with established CHD (50, 54). Primary outcomes included nonfatal myocardial infarction or CHD death. Secondary outcomes included other CHD events, vascular disease, cancer, thromboembolism, gallbladder disease, fractures, mortality, uterine bleeding, and other adverse effects. The trial ended after 4 years; study medication was stopped, although women were instructed to continue hormone therapy under the guidance of their physicians, and follow-up (HERSII) continued for a cumulative period of 6.8 years (52, 53). ESPRIT, which compared estradiol valerate with placebo, enrolled 1017 postmenopausal women who had just survived their first myocardial infarction (57). The primary outcomes were first nonfatal reinfarction, cardiac death, or death from another cause within 2 years of study entry. Secondary outcomes included uterine bleeding, endometrial cancer, breast cancer, stroke, other thromboembolic events, fractures, and adherence to treatment.
Two other trials provided limited results. The ULTRA trial (58) compared an ultra-low dose of transdermal estradiol (0.014 mg/d) with placebo to evaluate bone mineral density, clinical fractures, endometrial hyperplasia, urinary incontinence, and cognitive function. WISDOM (62) was designed to measure long-term outcomes of CEE plus MPA, primarily major cardiovascular disease events, osteoporotic fractures, and breast cancer. The study closed during the recruitment phase, follow-up was short, the power of the study was greatly reduced, and most outcomes were not obtained.
All trials met the criteria for fair quality. High attrition or low adherence to medications was the most common deficit (WHI [14, 28, 34], HERS [50, 54], and ESPRIT ). In the WHI estrogen plus progestin trial, 42% of participants in the hormone group and 38% in the placebo group stopped taking study medications during the trial (14, 28), whereas 54% discontinued therapy in the estrogen-only trial (34). For both WHI trials, the drop-in and drop-out rates exceeded design projections. The WHI trials (2, 3) and WISDOM (62) were discontinued prematurely because of adverse events. Other methodological limitations included differences between groups at baseline (WHIMS [44, 45], HERS [50, 54], and ULTRA ), small sample size (EMS ), short follow-up periods (WISDOM ), unclear ascertainment of some outcomes (WHISCA [47, 48], EMS , and WHI [15, 30, 36, 55]), and unblinding of treatment groups (WHI [2, 3] and HERS [52, 53]).
Benefits of Menopausal Hormone Therapy to Prevent Chronic Conditions
The results of the trials indicated benefits for women randomly assigned to hormone therapy that varied by regimen (Table 2 provides estimates of relative and absolute benefits). Women receiving estrogen only in the WHI trial had reduced incidence of invasive breast cancer (hazard ratio [HR], 0.77 [95% CI, 0.62 to 0.95]) (34) and reduced breast cancer mortality (HR, 0.37 [CI, 0.13 to 0.91]) (63). Colorectal cancer was reduced for women who received estrogen plus progestin (HR, 0.75 [CI, 0.57 to 1.00]) (28), although the results were of borderline statistical significance. Colorectal cancer was not reduced for women who received estrogen only in the WHI trial (34) or estrogen plus progestin in HERS (53).
The incidence of diabetes was reduced for women who received estrogen plus progestin in the WHI trial (HR, 0.79 [CI, 0.67 to 0.93]) (36) and in HERS (HR, 0.65 [CI, 0.48 to 0.89]) (55) but not in the WHI estrogen-only trial (15). Diabetes was diagnosed by self-report in the WHI trial and fasting glucose levels of 6.9 mmol/L or greater (≥124.3 mg/dL) in HERS.
Both estrogen plus progestin and estrogen reduced hip, vertebral, and total fractures in the WHI trials (28) but not in HERS (53). For estrogen plus progestin, estimates included HRs of 0.67 (CI, 0.47 to 0.95) for hip, 0.68 (CI, 0.48 to 0.96) for vertebral, and 0.76 (CI, 0.69 to 0.83) for total fractures (28). The results of the estrogen-only trial were similar (28).
Harms of Menopausal Hormone Therapy to Prevent Chronic Conditions
The results of the trials indicated several important adverse effects for women randomly assigned to receive hormone therapy (Table 2 provides estimates of relative and absolute risks for harms). Incidence of invasive breast cancer was reduced in the WHI estrogen-only trial but increased in the estrogen plus progestin trial (HR, 1.25 [CI, 1.07 to 1.46]) (18). Hormone users also had more abnormal mammography results, larger-sized tumors, and more advanced stages of breast cancer (18, 20). Other types of cancer, including lung, endometrial, ovarian, and cervical cancer, were not increased in the estrogen plus progestin trial (14, 21, 28), and lung cancer was not increased in the estrogen-only trial (19). Invasive breast, lung, and endometrial cancer were not increased in HERSII (53).
Contrary to the cardioprotective effects initially hypothesized by the WHI investigators, women randomly assigned to receive estrogen plus progestin in the WHI trial had increased incidence of CHD, including nonfatal myocardial infarction and CHD death (HR, 1.22 [CI, 0.99 to 1.51]), that was not statistically significant (28). Coronary heart disease was not increased in women randomly assigned to receive estrogen only (34).
Stroke was increased for both estrogen plus progestin (HR, 1.34 [CI, 1.05 to 1.71]) (28) and estrogen only (HR, 1.36 [CI, 1.08 to 1.71]) (34) in the WHI trials. Thromboembolic events were also increased in the WHI estrogen plus progestin (HR, 1.88 [CI, 1.38 to 2.55] for DVT and 1.98 [CI, 1.36 to 2.87] for PE ) and estrogen-only (HR, 1.47 [CI, 1.06 to 2.05] for DVT and 1.37 [CI, 0.90 to 2.07] for PE ) trials.
No statistically significant increases in all-cause mortality were observed in the WHI estrogen plus progestin (28) or estrogen-only (34) trials, HERSII (53), or ESPRIT (57). Death from breast cancer (HR, 1.96 [CI, 1.00 to 4.04]) (18) and lung cancer (HR, 1.71 [CI, 1.16 to 2.52]) (21) were increased for women in the WHI estrogen plus progestin trial, although results for breast cancer mortality were of borderline statistical significance.
Gallbladder disease was increased in both WHI trials (HR, 1.61 [CI, 1.30 to 2.00] in the estrogen plus progestin trial and 1.79 [CI, 1.44 to 2.22] in the estrogen-only trial), as were cholecystectomy and cholecystitis (23).
Measures of impaired cognitive function were increased for probable dementia (HR, 2.05 [CI, 1.21 to 3.48]) but not for mild cognitive impairment (45) in women in the WHI estrogen plus progestin trial. These measures were not increased in the WHI estrogen-only trial (44) or the ULTRA trial (61).
The incidence of overall urinary incontinence was increased for women in the WHI estrogen plus progestin (relative risk, 1.39 [CI, 1.27 to 1.52]) (30) and estrogen-only (relative risk, 1.53 [CI, 1.37 to 1.71]) (30) trials after 1 year of treatment. Further analysis indicated increased risk for different types of urinary incontinence, including stress, urgency, and mixed. In a subsample of estrogen plus progestin users who were continent at baseline but developed incontinence, incontinence persisted during 3 years of follow-up (30). Weekly, stress, and urge incontinence were increased among estrogen plus progestin users in HERS (weekly odds ratio, 1.6 [CI, 1.3 to 1.9]) (56), but urinary incontinence was not significantly increased in the ULTRA trial (60).
Variability of Outcomes in Population Subgroups
Subgroup analyses of results based on individual characteristics were restricted to age and a few comorbid conditions.
In the WHI estrogen plus progestin trial, breast cancer incidence did not significantly differ on the basis of age, BMI, Gail risk score (18, 20), or first-degree family history (26) but increased with previous use of oral contraceptives (20) or menopausal therapy with estrogen plus progestin (18, 20) and with current smoking (20). Age also had no effect on the relationship between hormone therapy and breast cancer incidence in the WHI estrogen-only trial (2), but risks were significantly reduced in women without a previous biopsy indicating benign breast disease or a family history of breast cancer (63).
Subgroup analyses of the WHI estrogen plus progestin trial indicated no statistically significant interactions between several risk factors, hormone therapy, and CHD, except for women with elevated levels of low-density lipoprotein cholesterol at baseline (35). Overall, CHD events were increased during the first year of the trial compared with later years (35). Similar analyses for the estrogen-only trial indicated that women with elevated levels of C-reactive protein at baseline who received estrogen had a greater risk for CHD, but the results of all other analyses were not statistically significant (33). An additional subgroup analysis of the 2 WHI trials indicated that women initiating hormone therapy within 10 years of menopause had a statistically nonsignificant reduction in CHD risk compared with an increased risk among women initiating therapy 20 or more years since menopause (38).
Risk for stroke was similar for all subgroups evaluated for the 2 WHI trials (28, 34). For thromboembolic disease, use of estrogen plus progestin increased the risks associated with older age, being overweight or obese, or having factor V Leiden (25). Analysis of subgroups in the WHI estrogen-only trial indicated no associations with venous thrombosis (24).
The protective effect of estrogen plus progestin on fractures did not differ by age, BMI, smoking status, history of falls, personal or family history of fracture, calcium intake, previous hormone therapy, bone mineral density, or fracture risk score in the WHI trial (17). No subgroup differences were found in WHIMS (42, 43). In the WHI trials, urinary incontinence was related to older age and increasing time since menopause (30). In HERS, urinary incontinence was not increased among estrogen plus progestin users younger than 60 years (56).
We found that 9 trials published since 2002 provided outcome data relevant to USPSTF recommendations for postmenopausal hormone therapy (Table 3). Trials included the 2 main WHI trials, 2 trials consisting of subsamples from the WHI trials (WHIMS and WHISCA), EMS, HERS, ESPRIT, ULTRA trial, and WISDOM. Only the WHI trials were designed and powered to evaluate the effectiveness of hormone therapy for primary prevention of several conditions that were the focus of this review. The WHI trials met criteria for fair quality, provided most of the estimates of benefits and harms, had 11 years of follow-up, and were most applicable to the target population. Although results of the other trials were consistent with the WHI trials for selected outcomes, they measured few outcomes and were often inadequately powered to detect potentially important differences among groups.
The results of the WHI trials indicated some benefits with hormone therapy. Women randomly assigned to estrogen plus progestin had fewer fractures (hip, 6 fewer per 10,000 woman-years; vertebral, 6 fewer per 10,000 woman-years; and total, 46 fewer per 10,000 woman-years) and fewer cases of diabetes (15 fewer per 10,000 woman-years) than those randomly assigned to placebo. Women randomly assigned to estrogen only had fewer fractures (hip, 7 fewer per 10,000 woman-years; vertebral, 6 fewer per 10,000 woman-years; and total, 56 fewer per 10,000 woman-years) and fewer cases of invasive breast cancer (8 fewer per 10,000 woman-years) and breast cancer deaths (2 fewer per 10,000 woman-years). Whereas fractures were a major predefined secondary outcome and were determined by clinical and radiographic criteria, diabetes was diagnosed on the basis of a less rigorous approach by using post hoc analysis of self-reports. In comparison, women in HERS who received estrogen plus progestin also had reduced risk for diabetes on the basis of blood glucose levels, but not reduced fractures.
The WHI trials also demonstrated several harms. Women randomly assigned to estrogen plus progestin had more cases of invasive breast cancer (8 more per 10,000 woman-years), stroke (9 more per 10,000 woman-years), DVT (12 more per 10,000 woman-years), PE (9 more per 10,000 woman-years), gallbladder disease (20 more per 10,000 woman-years), probable dementia (22 more per 10,000 woman-years), and urinary incontinence (872 more per 10,000 woman-years) and more deaths from lung cancer (5 more per 10,000 woman-years) than those randomly assigned to placebo. Women randomly assigned to estrogen only had more cases of stroke (11 more per 10,000 woman-years), DVT (7 more per 10,000 woman-years), gallbladder disease (33 more per 10,000 woman-years), and urinary incontinence (1271 more per 10,000 woman-years). Women in HERS who received estrogen plus progestin also had increased risk for urinary incontinence.
These results reflect updated estimates from the WHI trials that differ from initial results for some outcomes. For both WHI trials, initial results for invasive breast cancer were not statistically significant. After 11 years of follow-up, results indicated a statistically significant increased risk for breast cancer from estrogen plus progestin and decreased risk from estrogen only. Although the initial results for estrogen plus progestin indicated reduced risk for colorectal cancer and increased risk for CHD, the updated estimates were of only borderline statistical significance. Updated results for other outcomes did not substantially change from initial estimates. As expected, statistically significant results for outcomes related to ongoing hormone exposure, such as stroke, thromboembolism, and fractures, became nonsignificant during the postintervention period (14, 18, 28, 34). The HRs for breast cancer also decreased after estrogen plus progestin therapy was discontinued, although cases continued to accrue (22).
Subgroup analyses were not performed for women who had premature or surgical menopause or used various types, doses, and methods of hormone delivery. Subgroup analyses based on age and comorbid conditions lacked power for many of the comparisons and indicated few statistically significant differences. These included increased breast cancer for women who received estrogen plus progestin who had previously smoked or used oral contraceptives or postmenopausal estrogen plus progestin; increased CHD for women who received estrogen plus progestin and had high low-density lipoprotein cholesterol levels or who received estrogen only and had high C-reactive protein levels; increased thromboembolic disease for women who received estrogen plus progestin and were older or obese or had factor V Leiden; and increased urinary incontinence for older women who received either regimen. Subgroup analyses of CHD outcomes suggested that women who were 20 years or more since menopause or were aged 70 years or older had the highest risks and younger women had lower risk, although these differences were not statistically significant. Other than these findings, trials provided few results applicable to clinical decisions about selecting hormone therapy based on individual patient characteristics.
Our review has limitations. Few trials met our inclusion criteria, although the number of participants was large. Few outcomes were reported in more than 2 trials and measurements varied, limiting comparisons across trials. Most trials had high attrition or low adherence to medications, including the WHI trials, in which nearly one half of the participants discontinued therapy during the trial. Post hoc analysis, small sample sizes, and differential adherence rates also limited the interpretation of results. Our review was limited to trials published in English, although no relevant trials were identified from abstracts of non-English-language journals, additional citation searches, or expert reviewers.
Trial participants were generally aged 60 to 69 years, which restricts the applicability of our findings. Research directed at women who are transitioning through menopause or immediately postmenopausal (in other words, most current hormone users) would be useful. Although the U.S. Food and Drug Administration has approved various types, doses, and delivery methods of menopausal hormones with differing physiologic effects (1), prevention trials have largely focused on oral CEE. Additional research is needed to understand the effects of other hormonal agents on health outcomes.
Continuing research is needed on such long-term outcomes as cancer and death to fully understand the implications of hormone therapy. In the WHI estrogen-only trial, a statistically significant reduction in invasive breast cancer incidence and mortality among estrogen users was only recently reported after nearly 11 years of follow-up (34, 63), whereas the results of the estrogen plus progestin trial indicated an increase in breast cancer (18). It is unclear whether this discrepancy is due to the concomitant use of progestin, the differences between women who have had a hysterectomy and those who have not, or other reasons.
In conclusion, our update of evidence from trials published since 2002 indicates that both hormone therapy regimens decrease risk for fractures but increase risk for stroke, thromboembolic events, gallbladder disease, and urinary incontinence. Estrogen plus progestin also increases risk for breast cancer and probable dementia, whereas estrogen alone decreases risk for breast cancer.
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Copyright and Source Information
Source: This article was first published in Annals of Internal Medicine (Ann Intern Med 2012;157:1-10).
Disclaimer: The findings and conclusions in this document are those of the authors, who are responsible for its content, and do not necessarily represent the views of AHRQ. No statement in this report should be construed as an official position of AHRQ or of the U.S. Department of Health and Human Services.
Acknowledgment: The authors thank Andrew Hamilton, MLS, MS, for conducting literature searches; Rongwei Fu, PhD, for statistical assistance; and Amanda Brunton, BS, for assistance with preparing the manuscript.
Grant Support: By contract HHSA-290-2007-10057-I-EPC3, task order 3, from AHRQ.
Potential Conflicts of Interest: Dr. Nelson: Grant (money to institution): Agency for Healthcare Research and Quality; Support for travel to meetings for the study or other purposes (money to institution): Agency for Healthcare Research and Quality. Ms. Walker: Grant (money to institution): Agency for Healthcare Research and Quality. Disclosures can be viewed at www.acponline.org/authors/icmje/ConflictOfInterestForms.do?msNum=M11-1085.
Requests for Single Reprints: Heidi D. Nelson, MD, MPH, Oregon Evidence-based Practice Center, Oregon Health & Science University, Mailcode BICC, 3181 Southwest Sam Jackson Park Road, Portland, OR 97239-3098; e-mail, firstname.lastname@example.org.
Current author addresses and author contributions are available at http://www.annals.org.
AHRQ Publication No. 12-05168-EF-3
Current as of May 2012
Nelson HD, Walker M, Zakher B, Mitchell J. Menopausal Hormone Therapy for the Primary Prevention of Chronic Conditions: A Systematic Review to Update the USPSTF Recommendations. AHRQ Publication No. 12-05168-EF-3. May 2012. http://www.uspreventiveservicestaskforce.org/uspstf12/menohrt/menohrtart.htm