Associations between Personal Care Product Use Patterns and Breast Cancer Risk among White and Black Women in the Sister Study

BACKGROUND: Many personal care products include chemicals that might act as endocrine disruptors and thus increase the risk of breast cancer. OBJECTIVE: We examined the association between usage patterns of beauty, hair, and skin-related personal care products and breast cancer incidence in the Sister Study, a national prospective cohort study (enrollment 2003–2009). METHODS: Non-Hispanic black (4,452) and white women ([Formula: see text]) were examined separately using latent class analysis (LCA) to identify groups of individuals with similar patterns of self-reported product use in three categories (beauty, skin, hair). Multivariable Cox proportional hazards models were used to estimate hazard ratios (HRs) and 95% confidence intervals (CIs) for associations between product use and breast cancer incidence. RESULTS: A total of 2,326 women developed breast cancer during follow-up ([Formula: see text]). Among black women, none of the latent class hazard ratios was elevated, but there were [Formula: see text] cases in any category, limiting power. Among white women, those classified as “moderate” and “frequent” users of beauty products had increased risk of breast cancer relative to “infrequent” users [[Formula: see text] (95% CI: 1.00, 1.27) and [Formula: see text] (95% CI: 1.02, 1.30), respectively]. Frequent users of skincare products also had increased risk of breast cancer relative to infrequent users [[Formula: see text] (95% CI: 1.00, 1.29)]. None of the hair product classes was associated with increased breast cancer risk. The associations with beauty and skin products were stronger in postmenopausal women than in premenopausal women, but not significantly so. CONCLUSIONS: This work generates novel hypotheses about personal care product use and breast cancer risk. Whether these results are due to specific chemicals or to other correlated behaviors needs to be evaluated. https://doi.org/10.1289/EHP1480