24 December 2019 (updated 6 February 2020)
A recently published study evaluated the association between hair products and breast cancer risk.
The researchers surveyed women enrolled in the Sister Study – these women had a sister with a history of breast cancer but had not been diagnosed themselves. The study group included over 46,000 women, ages 35-74, enrolled between 2003 – 2009. Study participants were asked at enrollment about their history and frequency of hair product use (permanent dye, semi-permanent dye, and straighteners) within the previous 12 months. Mean follow up was 8.3 years, and 2794 participants were diagnosed with breast cancer during that time (5.9%).
The main findings included:
- 55% of participants used permanent hair dye at the time of enrollment
- Use of permanent hair dye was associated with a 45% increased risk of breast cancer in black women and a 7% increased risk in white women [Note – only 11.5% of the patients in the no-dye and 6.6% of patients in the permanent dye groups were Black]
- Risk of breast cancer increased with increased frequency of permanent dye use
- 9.9% of participants used hair straightening products, and use was associated with an 18% increased risk of breast cancer
- Risk of breast cancer increased with increased frequency of hair straightener use
- Nonprofessional application of dyes and straighteners to others was associated with increased breast cancer risk
- There was no association between the use of semi-permanent hair dyes and breast cancer
It is known that hair dyes and chemical straighteners contain some compounds which have estrogen-like activity, and some of the chemicals are known to cause cancer in animals, but studies in women have been inconsistent. As this was an observational study, a direct cause-and-effect relationship cannot be determined based on the results. All women in the study were at increased risk of developing breast cancer due to their family history, and many other risk factors, as well as details regarding specific hair product use, cannot be accounted for. In addition, the authors reported on relative risk, but did not document absolute increases in risk, and not all of the associations were statistically significant. The authors concluded that the results “provide evidence to support the relationship of hair dye and straightener use with breast cancer risk and highlight potential differences in associations by ethnicity.”
In his blog post reviewing this study, epidemiologist Gideon M-K noted that “While the headlines only reported the 45% increase that seemed the scariest, the absolute increase in risk was only about 0.05%. To put it another way, for every 10,000 women who never dye their hair, about 72 get breast cancer every year. For women who dye their hair every month, this rate goes up to about 77 in 10,000.”
Some may feel more comfortable controlling what they can, and therefore will decide to avoid the use of these products. However, just like many other studies that show associations between foods, chemicals, behaviors and cancer development, this study is far from conclusive.
*If you are not able to access the full study and would like a copy, please email me: contact at drattai dot com