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, <3%; HR = 0.96, 95% CI: 0.76-1.22). Use of perms (34% non-Hispanic white vs. 8% black women) and straighteners (10% non-Hispanic white vs 75% black women) at ages 10-13 years varied by race. An elevated HR for breast cancer was observed for frequent use of chemical straighteners (HR = 1.27, 95% CI: 0.98-1.65). Though based on small numbers, this association was most pronounced for ER- invasive (HR = 2.04, 95% CI: 0.98-4.24) and premenopausal breast cancer (HR = 2.18, 95% CI 1.27-3.74). Frequent use of perms was also associated with a higher risk of invasive breast cancer and ER- tumors (HR = 1.25, 95% CI: 1.00-1.57 and HR = 1.69, 95%CI: 0.96-2.98, respectively). Although product use varied by race, associations with breast cancer did not. Conclusions: Frequent use of chemical straighteners or perms during the ages of 10-13 years was associated with a higher risk of breast cancer. These results suggest that exposure to the chemicals in these hair products, especially during adolescence which may be an important biological window of susceptibility, may play a role in breast carcinogenesis. [ABSTRACT FROM AUTHOR]