Examination of factors influencing the racial disparity in fibroid incidence - PROJECT SUMMARY Uterine fibroids are the most common pelvic tumors in women of reproductive age, coming to clinical attention in one in four women. Although these smooth muscle tumors are non-malignant, fibroids are a significant medical problem, coming to clinical attention in one on four women and accounting for over 200,000 hysterectomies annually. Furthermore, fibroids consume a significant amount of health care resources, accounting for billions of dollars annually. Of note, fibroids are 2-3 times as common among Black women compared to White women. Despite significant quality of life and health care costs associated with fibroids, few modifiable, factors have been identified, nor is it understood why Black women are disproportionately affected. A major barrier to understanding the relative contributions of established and yet-to-be identified risk factors that may contribute to the fibroid difference is that no single study has adequate numbers of both Black and White women to apply advanced epidemiologic methods (e.g., mediation analyses, population attribute risks) to evaluate these differences. We propose to study women from two prospective U.S. cohorts — Black women from the Black Women’s Health Study (BWHS) and White women from the Nurses’ Health Study II (NHSII) — to identify factors that explain the differences in fibroid incidence between Black and White women. Among 59,000 participants (6,200+ newly diagnosed cases) in the BWHS and 116,429 (8,100+ newly diagnosed cases) in the NHSII, we will examine the following specific aims: Aim 1. Determine if established fibroid risk factors (e.g., parity, age at menarche, smoking, body size), which differ in prevalence or timing between Black and White women, contribute to racial differences in the risk of uterine fibroids. We will calculate race-specific population attributable fractions to identify the proportion of fibroids cases that are attributable to each risk factor and summarize the impact of differences in the distribution of fibroids risk factors by race on fibroids incidence using a novel average odds ratio method. Aim 2. Determine if environmental and neighborhood-level factors contribute to the racial differences in the risk of uterine fibroids. Aim 3. Estimate the contribution of multiple factors simultaneously to the fibroids incidence difference between Black and White women using multiple mediation analysis. Factors to be considered for inclusion into the mediation models include reproductive, lifestyle, psychosocial, and environmental factors. Given that more than 25% of all women experience fibroids, the potential health and economic impact of this study is substantial. Black women suffer disproportionately from fibroids, but the reasons for this difference are not understood. The identification factors that contribute to the racial difference in fibroid incidence could lay the groundwork for identifying strategies that would reduce fibroid incidence among all women.
