Evaluating Risk Factors for Differences in Fibroid Size and Number Using a Large Electronic Health Record Population

Objective: To evaluate individual characteristics of women with fibroids in relation to fibroid size and number.

Methods: This cross-sectional study involved 2302 women (black and white, age range 18-87) with image- or surgery-confirmed fibroids from the Synthetic Derivative, a database of de-identified demographic and clinical information from patient electronic health records (EHRs) from the Vanderbilt University Medical Center. We performed multivariate regression analyses on the following outcomes: volume of largest fibroid, largest dimension of all fibroids, and number of fibroids (single vs multiple). Candidate risk factors included age at diagnosis, body mass index (BMI), race, type 2 diabetes status, and number of living children (a proxy for parity). We assessed potential effect measure modification by race and both age and BMI using a likelihood ratio test.

Results: Black race was strongly associated with having multiple fibroids (adjusted odds ratio [aOR]: 1.83, 95% confidence interval [CI]: 1.49, 2.24) and larger fibroid volume (adjusted beta: 1.77, 95% CI: 1.38, 2.27) and greater largest dimension (adjusted beta: 1.28, 95% CI: 1.18, 1.38). Having multiple fibroids was most strongly associated with ages 43-47 (aOR = 3.37, 95% CI: 2.55, 4.46) compared with the youngest age group (ages 18-36). Having a larger number of living children was associated with having single a fibroid (aOR: 0.88, 95% CI: 0.78, 0.99).

Conclusions: Our findings suggest that different underlying etiologies are involved for women developing single versus multiple fibroids and small versus large fibroids. Studies are needed of the mechanisms by which these characteristics influence fibroid formation and growth.