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Changes in Women's Use of Hormones After the Women's Health Initiative Estrogen and Progestin Trial by Race, Education, and Income
Affiliations of authors: HealthPartners Research Foundation, Minneapolis, MN (FW); Center for Health Studies, Group Health Cooperative, Seattle, WA (DLM, KMN, DSMB); University of Washington, School of Public Health and Community Medicine, Seattle, WA (DLM, KMN, DSMB); Department of Ambulatory Care and Prevention, Harvard Medical School and Harvard Pilgrim Health Care, and Menopause Consultation Service, Harvard Vanguard Medical Associates, Boston, MA (MTC); Meyers Primary Care Institute, Worcester, MA (SEA); Kaiser Permanente, Denver, CO (CLH); Channing Laboratory, Brigham and Women's Hospital and Harvard Medical School, Boston, MA (KAC); HMO Research Network's Center for Education and Research on Therapeutics, US (KAC)
Correspondence to: Feifei Wei, PhD, HealthPartners Research Foundation, 8100 34th Ave. S, MS#21111R, Bloomington, MN 55425 (e-mail: feifei.wei{at}healthpartners.com).
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ABSTRACT |
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 TopNotes Abstract IntroductionMETHODSRESULTSDISCUSSIONReferences |
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Background: We examined the impact of race, education, and household income on changes in rates of discontinuation and initiation of hormone therapy before and after release of the Women's Health Initiative estrogen plus progestin trial results. Methods: We conducted an observational cohort study of 221 378 women aged 40–80 years enrolled in five health maintenance organizations to estimate the prevalence and rates of discontinuation and initiation of estrogen plus progestin and estrogen only between September 1, 1999, to June 31, 2002 (baseline), and December 31, 2002 (follow-up). We identified the census block group for each participant by geocoding her 2003 residential address. We categorized women into racial, education, and income groups based on the distribution of these characteristics in her community from year 2000 census data and the distributions of these characteristics within her HMO. Results: There were significant differences in estrogen plus progestin and estrogen only prevalence by race, education level, and household income, and in estrogen plus progestin initiation by race and education level, but not by household income at follow-up. However, there were no differences by community race, education, or household income in change in the prevalence of either hormone therapy use at follow-up or in the rates of hormone therapy discontinuation or initiation from baseline to follow-up. Conclusions: Given the wide spread media attention to the Women's Health Initiative estrogen plus progestin trial results, our findings suggest comparable dissemination of this information across diverse socioeconomic groups.
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INTRODUCTION |
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The Women's Health Initiative (WHI) estrogen plus progestin (EPT) trial found that EPT use was associated with increased risks of breast cancer, coronary heart disease (CHD), stroke, venous thromboembolism, and pulmonary embolism (1–3). The early-termination announcement of the EPT trial was released to the general public and medical communities on July 9, 2002 (1). The impact of these results on use of EPT and estrogen only (ET) has been profound (4–10). Overall use of EPT and ET is estimated to have decreased 46% and 28% (4,5,7,9,10).
Previous studies have documented significant variation in hormone therapy use by race, education, geographic area, and income (11–27). Although the WHI results were widely publicized, it is unclear how well the information penetrated into different communities and how women living in sociodemographically disadvantaged communities perceived them. In this study, we examined whether there were differences in the prevalence and rates of initiation and discontinuation of EPT and ET before and after the release of WHI EPT trial results by race, education, and household income, among women aged 40–80 years.
We hypothesized that women living in communities with a substantial proportion of nonwhites, non–college graduates, or families with incomes below the poverty level had less access to mass media and less contact with health providers and therefore would be less likely to discontinue EPT and ET following the release of the WHI EPT study results.
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METHODS |
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The study methods have been detailed elsewhere (4). This study was performed within the Cancer Research Network, a consortium of nonprofit health maintenance organizations (HMOs), and used the HMO Research Network's Centers for Education and Research on Therapeutics (CERT) Patient Safety Study Cohort (28). The CERT cohort is a representative sample of approximately 200 000 members per site, of any age, enrolled in the 10 participating HMOs. Eligibility criteria for this study included a pharmacy prescription benefit some time during the initial study period (January 1, 1999–June 30, 2001). We expanded the Patient Safety Cohort study through December 31, 2002, and constructed a dynamic cohort of 221 378 women aged 40–80 years from five of the participating HMOs: Kaiser Permanente Colorado, Denver, CO; Harvard Pilgrim Health Care, Boston, MA; Fallon Community Health Plan, Worcester, MA; HealthPartners, Minneapolis, MN; and Group Health Cooperative, Seattle, WA. Women were included in the study if they enrolled in the HMO between September 1999 and December 2002, and met eligibility criteria. A total of 221 378 women were included in the study.
The study was reviewed and approved by the human subjects committee from each participating institution and from the data coordinating center, Channing Laboratory, Boston, MA. Collaborative agreements prevent us from providing site-specific estimates.
Hormone Use
We used automated pharmacy data to estimate the prevalence of EPT and ET use and the rates of EPT and ET discontinuation and initiation. We used National Drug Codes to identify all dispensings for oral or transdermal estrogen or progestin filled during the study period (4). EPT users were designated as women who filled combination products or estrogen and progestin preparations, and ET users as women who filled estrogen preparations with no progestin fills. A woman was defined as a progestin user if she filled at least one progestin-containing prescription during the study period. We used the number of pills or patches dispensed to estimate the duration of each prescription and its runout date. A woman was considered a continuous user if her dispensing was refilled within 60 days of its runout date. Each successive dispensing set a new runout date.
Enrollment
HMO enrollment was captured using automated membership data. We considered women to be continuously enrolled as long as any enrollment lapse did not exceed 2 months.
Race, Education, Household Income
We identified the census block group in which each participant lived by geocoding her 2003 residential address (29–49). We defined this census block group as a woman's "community."
For each woman, we determined the proportion of women living in her community who were African American, Asian, white, or other race, from the year 2000 census data. We similarly determined the proportion of women in her community who were not college educated and whose1999 household income was below the poverty level. The Census defined the 1999 household income as the sum of income received in calendar year 1999 by all household members 15 years old and older, including household members not related to the householder, people living alone, and other nonfamily household members. For the census measure, a woman was below poverty level if her total household income was less than the poverty threshold specified for the applicable family size, age of householder, and number of related children under 18 (50).
We categorized the communities in which women lived into racial, education, and income groups based on her assigned proportions and the distributions of these proportions within her HMO. Specifically, we calculated separately for each HMO the average of these proportions, which represent the distributions of the census block group characteristics within each HMO. We then determined HMO site-specific thresholds to categorize the census block group where a woman lived that would maintain the overall distribution of these groups. For example, the average proportions of African Americans in the communities where site A participants lived was 4.8%. The corresponding 95.2 percentile of the distribution of the proportions of African Americans across all women in site A was 25%; meaning for a member of site A to be classified to an "African American" census block group, she needed to live in a census block group with 25% or more African Americans. We classified the racial groups sequentially. First, we classified the African American group based on their HMO-specific thresholds. Then, among the remaining women not classified as living in an African American census block group, we classified women in the Asian group, then the white group, and last the other group. Each woman could be assigned to only one racial group. We employed a similar method to classify the census block group where a woman lived as a "below college education," or "1999 household income below poverty level."
The range of thresholds used in individual HMOs for identifying the African American, the below-college educated, and the impoverished communities were 15 to 25, 41 to 48, 15 to 19, respectively. It should be stressed that this paper makes inference about the racial and socio-economic make-up of the communities women live in, not the women themselves.
Comorbidities
We included diabetes and cardiovascular disease in our multivariable model because we previously found these comorbidities were associated with higher EPT discontinuation rates post-WHI compared than for women without either comorbidity (9). We used the Chronic Disease Score (CDS), a validated measure of comorbidity constructed from 6 months of pharmacy data, to identify women with cardiovascular disease and/or diabetes (51). Cardiovascular disease and diabetes were not mutually exclusive; women with both conditions were counted for each condition. We have previously described our methodology in detail (9). In brief, we calculated a monthly CDS value for each woman. Once identified as having a specific comorbidity, a woman was coded as having it throughout the remaining follow up time.
Analysis
Our analyses required 7 months of enrollment data before study inclusion to allow sufficient run-in time for estimating true initiation rates. We excluded women from the analysis at disenrollment; however, if they reenrolled in the HMO during the study period, they rejoined the cohort after a 7-month run-in time to ensure accurate classification of hormone use.
We estimated baseline rates by combining data from September 1999 through June 2002, a period of relatively stable rates. We compared baseline rates to rates in December 2002 (5 months following the release of the WHI EPT results). We examined EPT and ET use separately. We used Poisson regression to model the incidence of initiation and discontinuation of EPT and ET at baseline and follow-up (December 2002, 5 months following the release of the WHI results), adjusting for age, HMO, and comorbidities of cardiovascular disease and diabetes. We also included interaction terms between time period (baseline or follow-up) and the race/SES variables to test whether changes in these rates post-WHI compared to pre-WHI differed by community race, education, and household income. To account for possible serial correlation among repeated observations within women, a transition model (52) was used, assuming a first-order Markov process. Specifically, we modeled EPT and ET use conditional on use–no use in the previous month, which is equivalent to modeling the incidence of initiation (use in one month given no use in the previous month) and discontinuation (no use in one month given use in the previous month). The relative risks (RRs) and corresponding 95% confidence intervals (CIs) compare the prevalence and incidence of initiation and discontinuation at follow-up (December 2002) to the baseline values within each risk group.
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RESULTS |
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Table 1 shows the distribution of age and comorbidity by race, education, and income levels. The age distribution was similar among all races. A higher percentage of older women (aged 60 and older) had below college education. Women in the oldest age group (aged 70–79) had the highest proportion with incomes below the poverty level, and women in the middle age group (aged 50–64) had the lowest proportion of poverty-level women. Cardiovascular disease and diabetes were more prevalent in African American women, in women with below college level education, and in women from households with incomes below the poverty level. The distribution of race (African American: 2.3%–5.2%, Asian: 2.3%–5.2%, white: 79.8%–89.6%, other 5.3%–12.2%), education (college or above: 54.7%–64.0%), and household income (1999 household income below poverty level: 6.9%–8.5%) varied among the five HMOs.
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Tables 2 and 3 show unadjusted rates of EPT and ET prevalence, initiation and discontinuation by socioeconomic status (SES), before (baseline) and after (post) July 2002. EPT prevalence declined 38%–44%, EPT initiation declined 31%–56%, and EPT discontinuation rates increased approximately two- to fourfold between the groups (Table 2). Changes in ET prevalence, ET initiation rates, and ET discontinuation rates, from baseline through follow-up, were in the same direction but of smaller magnitude than those for EPT (Table 3).
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) and after (post
) July 2002
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There were significant differences in EPT and ET prevalence by race, education level, and household income, and in EPT initiation by race and education level, but not by household income (Tables 4 and 5). However, there were no differences in change in the prevalence of EPT and ET use, or in the rates of EPT and ET discontinuation or initiation between post-WHI EPT trial and pre-WHI EPT trial by race, education, or household income.
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Controlling for age, HMO, cardiovascular disease and diabetes, the EPT and ET prevalences for women living in census block groups classified as nonwhite were significantly lower than for women living in census block groups classified as white. The EPT prevalence of women living in census block groups classified as having below college education was significantly lower than those with college or above education. In contrast, the ET prevalence of women with below college education was significantly higher than those with college or above education. The EPT and ET prevalence among women living in census block groups classified as below poverty income level were both significantly lower than those with above poverty income level.
The rates of EPT initiation after the WHI EPT trial among women living in census block groups classified as African American or other race were significantly lower than among women living in census block groups classified as white or Asian. The EPT initiation rate for women living in census block groups with below college education was significantly lower than for those with college or above education.
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DISCUSSION |
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TopNotesAbstractIntroductionMETHODSRESULTSDISCUSSIONReferences |
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Although previous studies have shown a significant reduction in EPT and ET after the early termination of the WHI's EPT trial, none have looked at whether there were differences in these measures by SES. In this analysis of data from five geographically distinct HMOs, we found that the changes in prevalence, initiation, and discontinuation after the release of WHI were similar regardless of race, education level, or household income. The lack of observed difference among the different groups was in contrast to our hypothesis. Several facts may explain our findings. First, the widespread reporting of the findings from the WHI was accessible to the public and communicated by the full complement of media. (1–3,53–55) Second, the WHI publication was decisive in concluding "this regimen should not be initiated or continued for primary prevention of coronary heart disease"(1). Third, all participants were enrolled in HMOs and thus had access to health care. The use of hormone therapy pre-WHI might indicate the adequacy of this access to medical care and information; thus, similar changes in prevalence and discontinuation rates might be expected regardless of race, education, or income level. Fourth, at all five HMOs, newsletters or updated guidelines were disseminated by November 2004, less than 5 months after the release of the WHI EPT results. Last, discontinuation and lack of initiation post WHI EPT trial may be as much, if not more, a product of clinician decisions rather than patient decisions, so the similar behavior of clinicians at HMOs, rather than differences in patient beliefs, may drive the similarities across groups.
Among women in the San Francisco Mammography Registry, the release of the WHI EPT results was found to be associated with a decline in the use of hormone therapy, and the associations were observed for women of all races (10). These results are consistent with ours.
Consistent with the literature, our study found that there were significant differences in overall EPT and ET prevalence by the racial, and socioeconomic makeup of the communities in which women live, supporting the representative nature of the sample studied (11,25–27). Several studies have reported that the odds of hormone therapy use increased as education levels increased (12,13,15,21,24,25,56–59); however, few studies have examined the relationship between education and type of hormone therapy used. Brett et al. (60) reported that 4.1%, 5.8%, and 4.8% of women without a high school diploma, with a high school degree or some college education, and with a baccalaureate degree or higher, respectively, were current ET users, whereas 3.5%, 9.3%, and 13.6%, respectively, were current EPT users among women 40 years of age without history of hysterectomy. In this study, we found that the EPT prevalence of women classified as having less than a college education was significantly lower than those with a college or higher education. On the contrary, we also found that the ET prevalence of women with less than a college education was significantly higher than those with college or higher education, suggesting differential hysterectomy rates in women of different educational backgrounds (61). Kjerulff et al. found that with adjustment for the effect of age, women without high school diplomas had hysterectomies at twice the rate of women with college degrees (62).
Our study has several limitations. Use of geocoding to assign the race, education, and household income level of the women provides information about the communities in which women live, and may result in misclassification at the woman level, although our findings are consistent with those in the medical literature. Census-based data on income and education at the block group, tract, and ZIP code level have been widely used as proxies for the SES of individuals in studies of health outcomes and health funds allocation (29–49). Census-based SES data at the block group and tract level have also been used to characterize community socioeconomic conditions (42–45). We have based our interpretation of the results on the characteristics of communities in which women live. Due to the possibility of misclassification, care should be taken when generalizing these results to the woman level.
Second, the generalizability of the results to other populations may be limited. Based on HMO newsletters or updated guidelines, there were various interventions to respond to the WHI results in place in all five participating HMOs by November 2004, less than 5 months after the release of the WHI EPT results. It is not clear whether interventions occurred as rapidly in non-HMO settings. Third, we used data in December 2002, 5 months following the release of the WHI EPT results. Longer follow-up may reveal different patterns of change (63). Fourth, we do not have access to potential confounding variables, such as menopausal symptoms, osteoporosis, and hysterectomy status.
The strengths of this study include using woman level data from a large random sample from five HMOs across the United States. Our findings should be generalizable to approximately one in four (26.4%) U.S. residents, as this is the proportion currently enrolled in HMOs in the United States (55), if not to the larger U.S. population. Our estimates were based on pharmacy dispensing rather than on self-reported data or on written prescriptions that may not have been filled. Although we could not capture hormone use if women filled at a pharmacy whose data were not captured in the HMO pharmacy database, one of the participating HMOs has previously reported that 95% of women aged 60–80 years reported filling all or almost all of their prescriptions at their HMO pharmacies, providing reassurance that this is not a major limitation (64). Filling a prescription has been shown to be a reasonably strong proxy for actually taking medication, as shown in the Harvard Pilgrim Health Care population (65).
In summary, we found that there were no differences in change in the prevalence of EPT and ET use and the incidence of EPT and ET discontinuation and initiation by race, education, or household income following the release of the WHI's EPT results. Given the widespread media attention to the WHI EPT trial results, our findings that different demographic groups appear to have an equivalent likelihood for ET and EPT discontinuation suggest comparable dissemination of this information across diverse SES groups. Future studies that show medication or procedures causing adverse outcomes may consider employing such knowledge to ensure that study results are received across SES.
In April 2004, release of the results from the WHI ET trial indicated no significant effect of ET on risks for coronary heart disease, breast cancer, colorectal cancer, pulmonary embolism, or total mortality, a 39% decrease in hip fracture risk, and a 40% increase in stroke risk (66). How these findings may influence subsequent rates of EPT and ET use remains to be determined.
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NOTES |
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Funded by a cooperative agreement from the National Cancer Institute (U19-CA-79689-05). Data collection for the Patient Safety Project was funded by a grant from the Agency for Healthcare Research and Quality (AHRQ U18HS11843-01). Dr. Buist's time was supported in part by a grant from the American Cancer Society (CRTG-03-024-01-CCE).
The Cancer Research Network (CRN) consists of the research programs, enrollee populations, and databases of 10 HMOs that are members of the HMO Research Network. The health care delivery systems participating in the CRN are: Group Health Cooperative, Harvard Pilgrim Health Care, Henry Ford Health System, HealthPartners, the Meyers Primary Care Institute of the Fallon Healthcare System/University of Massachusetts, and Kaiser Permanente in five regions (Colorado, Hawaii, Northwest [Oregon and Washington], Northern California, and Southern California). The overall goal of the CRN is to increase the effectiveness of preventive, curative, and supportive interventions that span the natural history of major cancers among diverse populations and health systems, through a program of collaborative research.
We thank Drs. Larry Kessler, Robert Davis, Martin Brown, Marsha Raebel, Andrea Z. LaCroix, Richard Platt and Edward Wagner, and Kevin Beverly, MA, Linda Shultz, MPH, Sarah Greene, MPH, and Dana Rickey for their assistance with this project. We also acknowledge all of the investigators who worked on the HMO Research Network Center for Education and Research on Therapeutics Patient Safety Project. We also acknowledge all of the programmers from participating sites who worked on the HMO Research Network Center for Education and Research on Therapeutics Patient Safety Project (Julia Hecht, PhD, GHC; Doris Milan, Harvard Pilgrim Health Care; Jackie C. Fuller, Meyers Primary Care Institute; David L. McClure, MS, KP Colorado; and Gerald Amundson, HealthPartners).
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