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Uterine leiomyomata (fibroids) are the leading cause of hysterectomy in the United States, accounting for >200,000 hysterectomies per year. Another 30,000 – 50,000 women with fibroids elect to have myomectomies in order to preserve their fertility. The resulting inpatient health care costs exceed $2 billion each year. An estimated 20% of black women and 7% of white women have hysterectomies to treat their fibroids. Despite the morbidity and high medical costs associated with fibroids, especially among black women, there has been little epidemiologic study of this condition. The causes of uterine fibroids are unknown, but they are hormone-dependent. They develop after puberty and regress after menopause. Both estrogen and progesterone are considered important stimulants, or at least permissive factors for tumor growth.
The NIEHS Uterine Fibroid Study was designed to identify risk factors for fibroids and assess factors related to symptom development. A randomly-selected sample of 35-49 year-old members of a Washington, DC-based prepaid health plan was approached for participation. From 1996-1999 we enrolled 1430 women (57% African American) and collected extensive questionnaire data on fibroid diagnoses, other medical conditions, reproductive, and exposure history. The premenopausal women were asked to have an abdominal and transvaginal ultrasound to determine their fibroid status, regardless of previous diagnoses. For premenopausal women we also collected a blood and a urine specimen and requested completion of a daily menstrual diary for 7 weeks. We followed symptom development and fibroid treatment in the premenopausal participants through 2004. Follow-up data were collected by telephone interview and retrieval of fibroid-related medical records.
We have described the age-specific incidence of fibroids for African American and white women, showing that African American women have earlier onset and higher age-specific incidence of this condition. Though we have identified several risk factors for tumor development, those factors do not explain the significantly higher risk in African Americans. Gene-environment interactions may play an important role. We have extracted DNA from blood samples, and hope to examine a series of hypotheses. For example, because fibroids are hormonally dependent tumors, polymorphisms in estrogen metabolism genes are prime candidates to examine as possible susceptibility factors that might interact with reproductive and exposure factors like parity and alcohol intake.
No prior research has identified fibroid status in a group of randomly selected women and followed them to evaluate the clinical significance of their fibroids and factors associated with symptom development. We will describe changes in symptoms over the follow-up time and examine hormonal, reproductive, and lifestyle factors that may be associated with symptom development for African American and white women. We will identify factors that place women at high risk of fibroid-related health problems. When preventive treatment options become available, early identification and treatment of high-risk women will reduce the need for surgical intervention.
