Uterine leiomyomas (fibroid tumors)

Several studies have found a higher prevalence of fibroid tumors among black women compared with white women. However, these studies evaluate women who are undergoing hysterectomy or myomectomy, which may not accurately represent the true distribution of fibroid tumors in the general population; racial and ethnic variation in disease severity, access to nonsurgical treatment, or treatment preferences may result in a higher prevalence of surgery among black women. One study attempted to overcome this limitation by screening randomly selected women who were 35–49 years old for fibroid tumors with pelvic ultrasound scans. After the data were adjusted for body mass index (BMI) and parity, black women were nearly 3 times as likely to have fibroid tumors compared with white women (odds ratio [OR], 2.7; 95% confidence interval [CI], 2.3–3.2). Two other studies included women who underwent surgical management of fibroid tumors and those who did not. Among 95,061 premenopausal participants in the Nurses Health Study II, black women had 3 times the odds of receiving a diagnosis of fibroid tumors by pelvic examination, ultrasound scans, or hysterectomy compared with white women (OR, 3.3; 95% CI, 3.0–4.3). Similarly, in an adjusted analysis from a case-control study of patients who received either surgical or medical management of fibroid tumors, black women had 9 times the odds of clinically apparent fibroid tumors (OR, 9.4; 95% CI, 5.7–15.7).

Although studies of patients who undergo surgery have significant limitations for estimating fibroid tumor prevalence, they are critical for exploring disparities in the surgical burden among women with fibroid tumors. In an uncontrolled nationwide analysis, the rate of hysterectomy for fibroid tumors was 37.6 per 10,000 black women compared with 16.4 per 100,000 white women. In a prospective cohort study of approximately 80,000 women in California, black women had a significantly higher rate of surgery for fibroid tumors, compared with non-Latina white women, in a model that controlled for age and family history of fibroid tumors (relative risk, 2.28; 95% CI, 1.81–2.87). Several smaller studies have confirmed this higher prevalence of fibroid tumors among black women who undergo hysterectomy and/or myomectomy.

In addition to a higher rate of fibroid tumors, several studies have found that black women are seen at a younger age, with larger, more numerous, and more rapidly growing fibroid tumors compared with white women. Huyck et al reported a mean age for fibroid tumor diagnosis of 31 years among black women and 37 years among white women ( P < .001). Three other studies have confirmed this finding, with black women receiving a diagnosis of fibroid tumors ≥3 years before white women. In a random sample of women, ultrasound scanning detected multiple focal fibroid tumors in 74% of black women but in only 31% of white women between the ages of 35–39 years. Peddada et al reported differential fibroid tumor growth by race; the likelihood of rapid tumor growth (>20% increase in volume per 6 months) increased with age in black women but declined with age among white women ( P = .004). Black women who undergo surgery for fibroid tumors may also have larger and/or a greater number of fibroid tumors compared with white women. Among hysterectomy patients, black women had a mean uterine weight of 421 g, compared with 319 g for white women, and black women who undergo myomectomy were more likely to have >4 fibroid tumors and less likely to have only 1 ( P = .001). However, these differences in fibroid tumor characteristics may be due to variation in patient preference for the timing of surgery, rather than true physiologic differences in fibroid tumor development.

Larger size and a greater number of fibroid tumors may result in worse symptoms and surgical outcomes for black women. A multivariable model that controlled for fibroid tumor risk factors showed that black women were more likely to have severe disease based on age at diagnosis, severity of menstrual symptoms, and history of fibroid tumor-related surgery (OR, 5.2; 95% CI, 2.0–13.7). In a study of 1200 women with fibroid tumors who underwent hysterectomy, black women were more likely to report severe pelvic pain (59% vs 41% for white women) and have anemia (56% vs 38% for white women). Roth et al reported that, among 225 women who underwent myomectomy, black women were twice as likely to have a complication compared with white women (OR, 2.5; 95% CI, 1.5–4.8) and more frequently required a blood transfusion (OR, 2.3; 95% CI, 1.1–5.0). However, these differences appeared to be related to the larger size, greater number, and increased comorbidities among black women. After controlling for these clinical factors, the risk of complications or blood transfusion was not significantly different between black and white women.

There are multiple possible causes for a higher prevalence and more severe presentation of fibroid tumors among black women. Fibroid tumors are hormonally responsive tumors, and some genetic studies have found that black women have unique gene polymorphisms for estrogen synthesis or metabolism and aberrant expression of micro-RNAs that may lead to gene dysregulation in fibroid tumors. For example, the estrogen receptor-α PP variant has a higher prevalence among black women and has been associated with an increased risk of fibroid tumors. One investigation found more polymorphisms in catechol-O-methytransferase, which is an enzyme that is involved in estrogen metabolism, among black women; another study did not confirm this finding. Lifestyle and clinical factors, such as diet, BMI, smoking, alcohol intake, exercise, diabetes mellitus, and hypertension, have also been reported in some studies to increase the risk of fibroid tumors. Higher rates of these risk factors among black women, compared with other racial and ethnic groups, may contribute to the incidence of fibroid tumors. Finally, exposure to bisphenol A has been found to have transcriptional activation and mitogenic effects on fibroid tumors in the Eker rat and CD-1 mouse models. Differential exposure to these or other environmental factors by race and ethnicity may contribute to variations in the prevalence of fibroid tumors.

There is scarce literature on differences in fibroid tumor presentation or treatment among racial and ethnic groups other than black and white women. In the Nurses Health Study II, there were no statistically significant differences in the likelihood of a fibroid tumor diagnosis among Hispanic and Asian women compared with white women. Conversely, Templeman et al, who applied similar multivariable models, found that Hispanic women had a higher risk of undergoing surgery for fibroid tumors compared with white women (OR, 1.3; 95% CI, 1.1–1.6). In this study, there were no significant differences in the prevalence of fibroid tumors between Asian and white women. Future research is needed to examine the prevalence, prognosis, and treatment of fibroid tumors among Hispanic and Asian women to clarify these preliminary findings. Studies are also needed to explore potential genetic causes of fibroid tumor development among Asian and Hispanic women, as have been found among black women.

Endometriosis

Endometriosis is a common estrogen-dependent condition that may cause dysmenorrhea, chronic pelvic pain, and infertility. The gold standard for diagnosing endometriosis is a biopsy of abnormal tissue visualized during surgery. Historically, many gynecologists believed that endometriosis was a disease that was confined almost exclusively to white women. Most early studies reported at least double the prevalence of endometriosis among white women, and many authors propagated the belief that endometriosis was a rare condition among black gynecology patients. In the 1970s, several studies reported that >20% of black women who underwent diagnostic laparoscopy had endometriosis and suggested that endometriosis was overlooked as a cause of pelvic pain because of clinicians’ misperceptions of the low incidence in black women However, this early literature was significantly limited by a lack of multivariable models to account for clinical and demographic factors that have been associated with a diagnosis of endometriosis.

More recent studies have had conflicting results for racial and ethnic differences in endometriosis. In a study of 330 women who underwent laparoscopic tubal sterilization that accounted for age, parity, income, and payment source in multivariable models, Asian women had almost 9 times greater odds of endometriosis (OR, 8.6; 95% CI, 1.4–20.1) compared with white women; the findings for black and Hispanic women were not statistically significant. Several other studies of women who underwent infertility evaluation or laparoscopy for pelvic pain have also reported an increase in the prevalence of endometriosis among Asian women compared with white women. However, in a prospective cohort study of 90,000 women who were enrolled in the Nurses Health Study II, Asian women did not have a statistically significant difference in the odds of self-reported endometriosis in a model that controlled for age, parity, and BMI (OR, 0.6; 95% CI, 0.4–0.9). In the same study, black and Hispanic women were each 40% less likely to be diagnosed with endometriosis (OR, 0.6; 95% CI, 0.4–0.9 for black women; OR, 0.6; 95% CI, 0.4–1.0 for Hispanic women). Two other studies have found no statistically significant differences in the prevalence of endometriosis between any racial or ethnic groups.

The heterogeneity in findings for differences in the prevalence of endometriosis by race or ethnicity may reflect the diversity of study designs. Some studies have focused on symptomatic patients with infertility or pelvic pain that may underrepresent medically underserved women in racial or ethnic minority groups with poorer access to gynecologic services. Other studies have assessed asymptomatic patients at the time of laparoscopy with variation in the design of multivariable models. Although the epidemiologic evidence is inconclusive, genetic studies have sought a cause for racial and ethnic differences in endometriosis. Some authors have identified gene mutations among Asian women that may make them more susceptible to endometriosis. However, a recent literature review found weak data to support an association between genetic polymorphisms and endometriosis. Additional research is needed to better understand possible genetic mechanisms that are associated with racial and ethnic differences in the prevalence of endometriosis. Endometriosis has also been associated with environmental exposures, such as in utero cigarette smoke and diethylstilbestrol, dioxin, and serum polychlorinated biphenyl congeners in some, but not all, studies. Racial and ethnic differences in these environmental exposures may contribute to variations in endometriosis. However, data are limited for serum levels of these chemicals among Asian women, compared with other groups. Further research is needed to elucidate possible racial and ethnic differences among women with endometriosis and to determine how these differences affect gynecologic outcomes.

Hysterectomy rates

Hysterectomy is the most common nonobstetric surgery among women in the United States, with approximately 600,000 procedures performed every year. Although some studies have found no association between race/ethnicity and the prevalence of hysterectomy, several large investigations have reported higher rates of hysterectomy among black women. In a nationwide analysis of hospital discharge data, black women were more likely to undergo hysterectomy (6.2 per 1000) than white women (5.3 per 1000) overall; these differences were particularly pronounced in women 40–44 years old, which is the most common age range for hysterectomy (16.8 per 1000 for black women; 10.8 per 1000 for white women). Similarly, among all women 40–49 years old in Maryland from 1986–1991, the rate of hysterectomy was 12.8 per 1000 for black women compared with 10.9 per 1000 for white women. Black women in the Coronary Artery Risk Development in Young Adults (CARDIA) study had 3 times the prevalence of hysterectomy compared with white women (12% vs 4%). Among a diverse sample of 15,160 women who were enrolled in the Study of Women Across America (SWAN), 30% of black women reported hysterectomy compared with 15% of white women.

Two studies have found significantly higher rates of hysterectomy among black women, irrespective of common clinical and demographic factors that are associated with undergoing hysterectomy. In the CARDIA study, black women were found to have nearly 4 times the odds of undergoing hysterectomy, compared with white women, after the data were controlled for BMI, polycystic ovarian syndrome, tubal ligation, depressive symptoms, age at menarche, education, access to medical care, geographic site, and a diagnosis of fibroid tumors (OR, 3.7; 95% CI, 2.4–5.6). In a subanalysis of 1144 women who reported a history of fibroid tumors, black women were still found to have a higher likelihood of hysterectomy (OR, 3.5; 95% CI, 2.2–5.4). In the SWAN study, black women were 1.7 times more likely to undergo hysterectomy (OR, 1.7; 95% CI, 1.5–1.9) after the data were controlled for education, geographic site, age, marital status, fibroid tumors, parity, smoking, and social support. Although these studies do not account for all possible confounding factors, they indicate that race appears to have a significant influence on hysterectomy rates after other demographic and clinical factors have been accounted for. Interestingly, in a diverse cohort of 1400 women with symptomatic fibroid tumors, abnormal uterine bleeding or pelvic pain, health-related quality-of-life outcomes, and attitudes regarding hysterectomy (rather than race or ethnicity) were independent predictors of undergoing hysterectomy. Further investigation regarding whether these issues may explain the increased rate of hysterectomy among black women is warranted.

Poorer access to hysterectomy alternatives or limited knowledge of nonsurgical treatments may contribute significantly to the higher rate of hysterectomy among black women. Black women may have lower health literacy, which results in less awareness of nonsurgical or minimally invasive options to manage common gynecologic conditions. In 1 qualitative study on hysterectomy in Texas, black women expressed strong desires to avoid or delay surgery for their gynecologic problem and advocated the use of alternative therapies. Therefore, it is possible that the higher hysterectomy rate reflects less access to nonsurgical therapies, despite the desire to avoid hysterectomy. In an evaluation of the appropriateness of hysterectomy among 2425 patients, black women were more likely to undergo hysterectomy that was classified as “inappropriate,” compared with white women. This association was primarily due to the high risk of inappropriate hysterectomies for women with fibroid tumors, irrespective of race. The hysterectomy rate in black women may therefore represent general overuse of a highly discretionary surgical procedure.

There are conflicting data on hysterectomy rates among Hispanic women. Many nationwide surveys collect race data in lieu of ethnicity categories, which significantly limits analyses of Hispanic women. In a cross-sectional study of approximately 25,000 women who were enrolled in the National Health Interview Survey, 12% of Hispanic women had undergone hysterectomy compared with 23% of non-Hispanic white women. When the data were controlled for multiple demographic and clinical factors, Hispanic women had a 64% lower odds of hysterectomy compared with non-Hispanic white women of similar education level (OR, 0.4; 95% CI, 0.3–0.4). However, Hispanic women had increased odds of hysterectomy in multivariable models (OR, 1.6; 95% CI, 1.3–2.1) in the SWAN study. These disparate findings may be related to differences in acculturation and/or primary language spoken between the study populations.

The literature is extremely limited on the prevalence of hysterectomy among Asian women, because many studies incorporate Asian women into an “other” race category, rather than create a distinct racial grouping. The SWAN study enrolled 1485 Asian women and found that 7% had a history of hysterectomy compared with 15% of white women. After clinical and sociodemographic factors had been accounted for, Asian women had a 56% decreased odds of undergoing hysterectomy (OR, 0.4; 95% CI, 0.3–0.6). In a subanalysis of SWAN participants who were enrolled in a single health maintenance organization, Chinese American women were significantly less likely to report a hysterectomy (OR, 0.6; 95% CI, 0.4–0.98). Acculturation, which is the adoption of behaviors and beliefs of the dominant culture, may influence the hysterectomy rate among Asian women; Chinese American women who were educated in China and possibly less accustomed to the routine use of hysterectomy in the United States had the lowest likelihood of hysterectomy compared with all other groups.