Adolescent Use of Hair Dyes, Chemical Straighteners and Perms in Relation to Breast Cancer Risk in the Sister Study

Hair products may contain hormonally active and carcinogenic compounds. We evaluated the risk of breast cancer associated with adolescent use of hair dyes, chemical straighteners and perms in a large prospective U.S. cohort. Methods: Sister Study participants (n = 47,833) were ages 35–74 years and had a sister who had been diagnosed with breast cancer at the time of enrollment (2003–2009). Enrollment questionnaires obtained information on demographics and lifestyle factors as well as frequency of use of hair dyes, chemical straighteners, and perms at ages 10–13 years. Cox proportional hazards models were used to estimate adjusted hazard ratios (HRs) and 95% confidence intervals (95% CIs) for the association between adolescent hair product use and breast cancer risk (invasive cancer and ductal carcinoma in situ). We considered whether associations varied by invasiveness, estrogen receptor (ER) status of the tumor, menopause status and race. Results: Over an average of 8.3 years of follow-up, 2,829 cases were diagnosed. Hair dye use at ages 10–13 years was uncommon and not associated with breast cancer risk (e.g. permanent hair dye,