Environmental Factor, December 2008, National Institute of Environmental Health Sciences
Fibroids and the Black Women's Health Study
By Robin Arnette
Lauren A. Wise, Sc.D., an Assistant Professor of Epidemiology at the Boston University School of Public Health, visited NIEHS recently to talk about her work on uterine leiomyomata, also known as "fibroids." Wise presented "Risk Factors for Uterine Leiomyomata in the Black Women's Health Study" during the Epidemiology Branch seminar held on November 3. The talk took place in Rodbell Auditorium and was hosted by Mitch Eddy, Ph.D., a senior investigator in the Laboratory of Reproductive and Developmental Toxicology.
Wise (http://sph.bu.edu/index.php?option=com_sphdir&id=239&Itemid=340&INDEX=9104) said that fibroids were benign tumors that arose from smooth muscle cells of the uterus in women. She explained that many fibroids were asymptomatic and didn't cause major morbidity, but they could be a huge problem for some women. Symptoms included menorrhagia or heavy menstrual bleeding, pelvic pressure, pain, infertility, reproductive dysfunction and complications in labor and delivery.
Wise also revealed the toll that fibroids exact on the nation's healthcare system. "Fibroids are the fifth leading cause of hospitalization for nonpregnancy-related conditions in reproductive-aged women and the leading cause of hysterectomy," she said. "This means they account for high healthcare costs - over $2.1 billion each year in the U.S."
Wise's interest in studying these tumors began during her days as a doctoral student at Harvard when she analyzed data from the Black Women's Health Study (BWHS) for her dissertation. Conducted by investigators from Boston University and Howard University, the study examined why black women tend to be disproportionately affected by certain illnesses, including breast cancer, diabetes, and fibroids.
"Black women have two to three times the incidence of fibroids compared to white women," Wise said. "This has been documented not only in the Nurses' Health Study II, an ongoing U.S. prospective cohort study, but also by a study by Donna D. Baird, Ph.D. (http://www.niehs.nih.gov/research/atniehs/labs/epi/women/index.cfm) Black women have an earlier age of diagnosis and hysterectomy, and they have larger and more numerous tumors at the time of diagnosis."
The BWHS started in 1995 and is a prospective cohort study of 59,000 black women aged 21-69 at baseline. The team enrolled participants through mailed questionnaires sent to subscribers of Essence Magazine and members of black professional health organizations. The questionnaires posed a series of questions dealing with demographics, lifestyle, anthropometric factors, reproductive and medical history, and diet. The team relied on self-reported diagnoses of fibroids confirmed by ultrasound, a noninvasive screening procedure with high sensitivity and specificity relative to histologic evidence. The data were updated every two years, and the cohort retention rate was approximately 80 percent.
Wise and her colleagues found an inverse association between age of menarche (i.e., first menstrual period) and fibroids. Women who started their periods at age 15 or older had a 30 percent decreased risk of developing fibroids compared with women who started menstruating at age 11 or younger. The team also found a 30 percent reduced risk of developing fibroids in women who have had children relative to women who had not given birth. Both findings may be explained by hormonal mechanisms, as fibroids are thought to be hormone-dependent tumors. "Women who have a later age at menarche or who have babies tend to have fewer menstrual cycles and, therefore, a reduced cumulative exposure to endogenous estrogens, which appear to promote fibroid growth," she said.
The BWHS also examined whether alcohol and smoking were possible risk factors for fibroids. Although Wise and colleagues published data showing a weak positive association between alcohol consumption and fibroids, and a weak inverse association between smoking and fibroids, repeated analysis after 6 additional years of follow-up yielded a stronger association with pack years of smoking staving off fibroids. Wise added, "Of course we wouldn't recommend that women start smoking to prevent fibroids, but it is an interesting finding from an etiologic point of view."
Wise's future research goals include examining environmental and early life exposures, diet, and genetics in relation to uterine fibroids.