ABSTRACT & COMMENTARY
Chemical Hair Treatments May Pose Highest Cancer Risk to Black Women Results from an observational cohort study REFERENCE
Eberle CE, Sandler DP, Taylor KW, White AJ. Hair dye and chemical straightener use and breast cancer risk in a large US population of black and white women. Int J Cancer. 2020;147(2):383-391. STUDY OBJECTIVE
To examine the association between use of hair dyes and chemical hair treatments and risk of breast cancer and to examine the differences in risk based on race/ethnicity DESIGN
Observational, prospective cohort study PARTICIPANTS
Participants from the Sister Study cohort, which was originally a group of 50,884 women aged 35 to 74 years from the United States who had been recruited between 2003 to 2009 and who had no personal history of breast cancer but had a sister who had been diagnosed with breast cancer. Total cohort used for analysis was 46,709, with the following subgroups: • White, non-Hispanic=39,261 • Black=4,087 • Hispanic=2,041 • Other=1,220 STUDY PARAMETERS ASSESSED
The study assessed whether individuals had been exposed to personal or nonprofessional application of permanent and semipermanent hair dye, as well as chemical relaxer/ straightener treatments, and with what frequency. Participants answered questionnaires regarding their hair product use over the past 12 months
from the time of enrollment. They were asked whether they had used dark colors (black, brown, auburn/ dark red); light colors (blonde, light red); or both. Researchers collapsed data for duration of use into categories of less than 5 years or greater than 5 years, with the latter considered long duration use. PRIMARY OUTCOME MEASURES
The incidence of breast cancer diagnoses among the participants were reported up until 2016 and measured against their exposure to various hair treatments. KEY FINDINGS
The majority of participants reported using hair dye at the time of enrollment (55%, or 25,887 participants). There were 2,794 cases of breast cancer identified over a mean follow-up period of 8.3 years. Use of permanent hair dye was associated with a 45% increase in breast cancer risk in Black women (HR=1.45, 95% CI: 1.10–1.90), and a 7% increase in White women (HR=1.07, 95% CI: 0.99–1.16; heterogeneity P=0.04). Hair straightener use across the entire cohort was associated with an 18% increased risk, and the frequency of self-use of straightener correlated with increasing risk (P for trend=0.02). For those administering dyes and straighteners to others (non-professionals), the application of semipermanent dye was associated with a 28% increased risk (HR=1.28, 95% CI: 1.05–1.56), and application of straightener was associated with a 27% increased risk (HR=1.27, 95% CI: 0.99–1.62).
6 ©2020 NATURAL MEDICINE JOURNAL. ALL RIGHTS RESERVED. NMJ, OCTOBER 2020 SUPPLEMENT—VOL. 12 , NO. 101 (SUPPL)
By Maxwell Crispo, ND PRACTICE IMPLICATIONS This study suggests that the use of chemical hair treatments increases cancer risk—specifically breast cancer risk—in women, regardless of ethnicity. With the number of known endocrine disruptors (along with other toxic ingredients) in both salon and at-home hair treatment products,1 environmental medicine advocates have been warning of the carcinogenicity of chemical hair treatments for many years. And while some integrative health practitioners may have been telling their patients to avoid these beauty practices or switch to more natural alternatives, the evidence in support of that claim has not necessarily “matched colors” with a number of previous studies finding no associated cancer risks from conventional hair treatments.2,3 However, the large sample size of this study, combined with the reasonable length of follow-up (7-13 years), allows for better statistical analysis than previously possible with small cohorts and case-control studies. The results of this study suggest that women increase their risk of breast cancer when they are exposed to permanent hair dye or chemical straightener compared to women who do not use these treatments at all. These results, combined with other case-controlled studies,4,5 provide clinicians reason to counsel patients about the use of these agents and the possible increased breast cancer risk. The results of this study suggest that women increase their risk of breast cancer when they are exposed to permanent hair dye or chemical straightener compared to women who do not use these treatments at all. (continued on page 8)
