Use of Hormone Replacement Therapy by Postmenopausal Women in the United States

Postmenopausal hormone replacement therapy (HRT) is a subject of major interest in the field of women's health. Although HRT has a clear role in the treatment of menopausal symptoms (1), uncertainty exists about its long-term use to prevent disease and prolong life (2). In randomized, controlled trials, HRT has been shown to improve lipid profiles (3) and increase bone density in postmenopausal women (4) but not to decrease the rate of subsequent coronary events in women with established coronary artery disease (5). Observational studies have shown that women who use HRT have a substantially decreased risk for coronary artery disease (6-8), osteoporosis and fractures (8-10), and death (12), but they may also have an increased risk for breast cancer (13). In 1992, guidelines from the American College of Physicians advised that postmenopausal women who have had hysterectomy and women at risk for coronary heart disease are likely to benefit from preventive HRT (14, 15). A more recent decision analysis suggested that almost all postmenopausal women will benefit from HRT, especially those with risk factors for coronary heart disease (16). Despite these recommendations, the benefits and risks of HRT are not fully defined. The decision to use preventive HRT is usually not simple and is probably influenced by the personal characteristics and beliefs of women and their physicians. Previous studies have sought to characterize women who use postmenopausal HRT (17-27), but most of these studies examined local or highly selected cohorts of patients. A recent report on HRT use in a national sample of women in the United States analyzed past and current use together and last collected data in 1992 (26). To our knowledge, only one study has assessed psychological factors that may influence the decision to use HRT (27). Therefore, we examined patterns of HRT use in a national sample of postmenopausal women during 1995 to understand how sociodemographic, clinical, and psychological characteristics were associated with current use of this treatment. We also assessed patterns of use in women at risk for cardiovascular disease who may benefit most from this therapy. Finally, we sought to identify potential selection effects that may be present in observational studies while randomized clinical trials of this therapy are in progress (28). Methods Study Sample In 1995, the John D. and Catherine T. MacArthur Foundation Research Network on Successful Midlife Development conducted a random-digit telephone survey of a probability sample of adults in the United States from 25 to 74 years of age to identify physical, psychological, and social factors that promote good health, psychological well-being, and social responsibility. The study protocol was approved by the human subjects committee of Harvard Medical School. The survey was conducted by using a multistage sampling design. For the first stage, an equal probability sample of telephone numbers, stratified by county in proportion to population, was selected from more than 70 million directory-listed residential numbers. After determining household eligibility, respondents were selected on the basis of age and sex and were offered a stipend for participation. The response rate for this telephone survey was 70%. United States Census data from 1990 for each telephone exchange were used to assess for response bias, and no statistically significant differences were found between eligible households for which the telephone interview was completed and other households by age, education, income, Hispanic ethnicity, other ethnicity, and residence in a Metropolitan Statistical Area. Participants who completed the telephone interview were also mailed a self-administered questionnaire. We limited our cohort to women 50 to 74 years of age; 93% of these women also completed the self-administered questionnaire and were eligible for our sample, yielding an estimated response rate of 65% for the combined telephone survey and questionnaire. Compared with women who responded to the telephone interview only, these women were younger (mean age, 60.1 compared with 62.7 years; P=0.02), more likely to be married (56% compared with 35%; P=0.004), and more likely to have completed at least 12 years of education (84% compared with 61%; P=0.001). From this cohort (n=668), we identified all postmenopausal women with no personal history of breast cancer (n=495). A woman was considered postmenopausal if she reported that her menses had stopped permanently. Because by 50 years of age, most women with a uterus in our sample had undergone natural menopause, women who had undergone hysterectomy were considered postmenopausal whether or not they had undergone bilateral salpingo-oophorectomy. Data Collection Current users of HRT were women who reported use of hormone replacement, such as estrogen, in the past 30 days. Women were also asked about sociodemographic, clinical, and psychological factors that had previously been associated with use of HRT in other studies or that we postulated might influence its use. Sociodemographic variables included age (denoted by indicator variables for 5-year increments), ethnicity (white or nonwhite), education (<12 years, high school graduate or general education diploma, or college graduate), household income (in quartiles), marital status (currently married), children (one or more), employment status (full-time job), rural residence (not living in a Metropolitan Statistical Area), and geographic region (Northeast, Midwest, South, and West) as defined by the U.S. Census. Clinical variables included a history of hysterectomy, having a regular physician, use of supplemental calcium, physical activity (vigorous activity one or more times per week), and a waist-to-hip ratio of 0.85 or less as a measure of body habitus; all of these factors were previously associated with use of HRT. We also examined self-report of diabetes, cigarette smoking (current, former, or never smoker), family history of myocardial infarction, hypertension, high cholesterol level, personal history of myocardial infarction or angina (based on the Rose criteria [29]), sexual activity, alcohol use, multivitamin use, and use of alternative therapies. Psychological variables included perceived risk for heart disease and cancer (above average compared with average or below), self-perceived physical and mental health (excellent, very good, or good compared with fair or poor), depression (based on the Composite International Diagnostic Interview [30]), self-report of depression or anxiety, perceived control over health, and thought and effort put into health. Women were also asked whether they worry about becoming less attractive or developing illness as they age. Measures of six major personality characteristicsagency (self-confident, forceful, assertive, outspoken, and dominant), agreeableness (helpful, warm, caring, softhearted, and sympathetic), openness (creative, imaginative, intelligent, curious, sophisticated, and adventurous), neuroticism (moody, worrying, nervous, and not calm), extroversion (outgoing, friendly, lively, active, and talkative), and conscientiousness (organized, responsible, hardworking, and not careless)were adapted from standard scales (31-34). Finally, we used the Somatic Amplification Scale (35) to assess somatosensory amplification (experiencing somatic sensation as intense, noxious, and disturbing). Statistical Analysis Data were weighted to adjust for differing probabilities of contacting households, sampling persons within each household, and obtaining completed surveys from designated participants (36) and to approximate the U.S. population on the basis of the Current Population Survey (October 1995). First, we adjusted for differing probabilities of successfully contacting households in geographic areas by mapping 1990 U.S. Census data on age, ethnicity, income, education, and urban location to telephone exchanges. Second, we adjusted for the higher probability of sampling persons in smaller households when their household was contacted. Third, we adjusted for differing probabilities of obtaining self-administered questionnaires from persons who completed the telephone interview by using numerous variables from the telephone interview. Finally, we created post-stratification weights so that the sample more closely approximated the U.S. population on the basis of 1995 Current Population Survey data. Thus, the weighted sample resembles the U.S. population by geographic region, ethnicity, age, education, marital status, and residence in a Metropolitan Statistical Area. We used the Pearson chi-square test to compare rates of HRT use by categorical variables and the Mantel-Haenszel chi-square test for the same comparison after stratifying by hysterectomy status (37). We converted values of each continuous psychological variable to ranks and compared users and nonusers of HRT by using two-way analysis of variance to control for hysterectomy status. We conducted multivariable logistic regression analyses in two stages. Because we had large numbers of sociodemographic, clinical, and psychological variables, we first created three separate models for each of these types of variables. Each model included all variables of a particular type with a P value of 0.2 or less in bivariable analyses. Finally, all variables with P values of 0.2 or less in the intermediate models were included in a final composite main-effects model. Because we also wished to ensure that the final model controlled for key demographic and clinical variables that might confound the effect of statistically significant variables, we also forced the following select variables to enter the final model: ethnicity, marital status, waist-to-hip ratio, income, hypertension, high cholesterol, family history of myocardial infarction, smoking, and personal history of coronary artery disease . Only this final composite multivariable logi