Age-specific incidence rates for self-reported uterine leiomyomata in the Black Women's Health Study

OBJECTIVE: Uterine leiomyomata represent a major public health problem for black women in the United States, but limited data are available on age-incidence curves in this high-risk population. We estimated overall and age-specific incidence rates for self-reported uterine leiomyomata in a large cohort of African-American women in the United States. METHODS: Data were derived from the Black Women's Health Study, an ongoing prospective cohort study of 59,000 black women from across the United States who were aged 21-69 years at baseline (ie, 1995). From March 1997 through March 2001, we followed up 22,895 premenopausal women with no prior diagnosis of uterine leiomyoma. Poisson regression was used to estimate overall and age-specific incidence rates and 95% confidence intervals (CIs) for self-reported uterine leiomyoma. In a subset of 248 patients who were selected randomly from the total case group, the self-reported diagnosis was verified in 96% of cases who released their medical records. RESULTS: During 76,711 woman-years of follow-up, 2,637 incident cases of uterine leiomyomata reported as confirmed by pelvic examination (n = 358), ultrasonography (n = 2,006), or hysterectomy (n = 273) were observed. Incidence rates per 1,000 woman-years were 34.4 (95% CI 33.1-35.7) for all cases combined, 29.7 (95% CI 28.5-30.9) for cases confirmed by ultrasonography or hysterectomy, and 3.6 (95% CI 3.2-4.0) for cases confirmed by hysterectomy. The incidence rate peaked at ages 40-44 years for all cases combined (incidence rate 45.6, 95% CI 42.0-49.5) and for cases confirmed by ultrasonography or hysterectomy (incidence rate 39.8,95% CI 36.5-43.4), and peaked at ages 45-49 years for cases confirmed by hysterectomy (incidence rate 8.3, 95% CI 6.4-10.7). CONCLUSION: Overall incidence rates for self-reported uterine leiomyomata were consistent with other U.S studies in black women and confirmed a high burden of disease in this population. Age-specific incidence rates showed a later peak incidence than that observed among U.S. black women in previous studies.