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Untangling Link Between Hair Relaxers and Breast Cancer Risk in Black Women

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Overall, there seems to be no link between hair relaxers and breast cancer risk in Black women. But some evidence suggests that heavy use of hair relaxers containing lye may be linked to a higher risk of estrogen-receptor-positive breast cancer, according to the Black Women’s Health Study.

The research was published on May 20, 2021, by the journal Carcinogenesis. Read the abstract of “Hair product use and breast cancer incidence in the Black Women’s Health Study.”

About the Black Women’s Health Study
About hair relaxers and breast cancer risk in Black women
About the study
What this means for you

About the Black Women’s Health Study

Started in 1995, the Black Women’s Health Study aims to find out why Black women have higher rates of a number of diseases, such as breast cancer at a young age, high blood pressure, diabetes, stroke, and lupus.1 Run by the Slone Epidemiology Center at Boston University, the study includes 59,000 participants and is working to better understand the causes of these illnesses.

When they joined the study in 1995, the women filled out questionnaires that asked about their medical conditions, lifestyle choices, and childbearing history, as well as demographic information. The women continue to fill out the questionnaires every other year.

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About hair relaxers and breast cancer risk in Black women

While the lifetime risk of breast cancer is similar for white and Black women, Black women are more likely to be diagnosed when they are younger and with more aggressive breast cancer subtypes, such as triple-negative. Black women are also more likely to die from breast cancer than white women.

Triple-negative breast cancer is:

  • estrogen-receptor-negative
  • progesterone-receptor-negative
  • HER2-negative

This means that triple-negative disease growth isn’t caused by either the hormones estrogen and progesterone or the presence of too many HER2 receptors. As a result, triple-negative breast cancer doesn’t respond to hormonal therapy or therapies that target HER2 receptors.

Between 10% and 12% of breast cancers — more than one out of every 10 — are triple-negative. Triple-negative breast cancer is typically more aggressive than other types of breast cancer.

Black women are much more likely than white women to use hair relaxers and straighteners, as well as leave-in conditioners. Many of these hair products contain estrogen or chemicals called hormone disrupters. Hormone disruptors can affect how estrogen and other hormones act in the body — by blocking them or mimicking them — which throws off the body’s hormonal balance.

Because extra estrogen can cause hormone-receptor-positive breast cancer to develop and grow, researchers have wondered if these hair products could increase breast cancer risk.

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About the study

Using information collected by the Black Women’s Health Study, the researchers looked at how often the women used hair relaxers between 1997 and 2017, as well as the type of hair relaxer they used. The researchers then looked to see if there were any links between hair relaxer use and breast cancer risk.

This analysis included information from 50,543 women.

In their analysis, the researchers excluded women who had been diagnosed with breast or other cancer in 1997 and women who had a history of breast cancer but whose year of diagnosis was unknown.

For this study, the researchers broke hair relaxer use into the following four categories:

  • never used
  • light user: used for 1 to 4 years, two or fewer times per year
  • moderate user:
    • used for 1 to 4 years, more than three times per year
    • used for 4 to 14 years, any frequency per year
    • used for 15 or more years, less than seven times per year
  • heavy user: used for 15 or more years, seven or more times per year

The researchers found that of all the women in the study:

  • 70% were moderate users
  • 20% were heavy users
  • 5% were light users
  • 5% were never users

Among the moderate and heavy users:

  • 37% used hair relaxers for 20 or more years
  • 33% used hair relaxers seven or more times per year
  • 34% reported at least five burns
  • 64% said they first started using hair relaxers before age 20

The researchers also found that 71% of the women used relaxers that didn’t contain lye, 16% used relaxers containing lye, and 13% didn’t know which type of relaxer they used.

Of the 2,311 women who were diagnosed with breast cancer between 1997 and 2017:

  • 1,843 had invasive cancers
  • 468 had ductal carcinoma in situ (DCIS)

Among the 2,311 cancers diagnosed:

  • 1,420 were estrogen-receptor-positive
  • 601 were estrogen-receptor-negative
  • 286 were triple-negative

The researchers compared breast cancer rates among women who were moderate or heavy users of hair relaxers with cancer rates among women who were light users or never used hair relaxers.

Overall, the researchers found no association between an increase in breast cancer risk and using hair relaxers.

Still, the results suggested that heavy users of hair relaxers containing lye may have an increased risk of estrogen-receptor-positive breast cancer.

“…Our results are generally reassuring: we found no clear evidence that hair relaxer use is associated with breast cancer risk for most women,” lead author Kimberly Bertrand, ScD, assistant professor of medicine at Boston University School of Medicine, said in a statement. “However, there was some evidence the heaviest users of lye-containing products — those who used these products at least seven times a year for 15 or more years, which represented approximately 20% of women in our study — had about a 30% increased risk of estrogen-receptor-positive breast cancer.”

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What this means for you

If you’re a Black woman who is a light or moderate user of hair relaxers, this study offers some reassuring news.

But if you’re a Black woman who is a heavy user of relaxers containing lye, the results are troubling.

It makes sense to talk to your doctor about this study’s results and also about how often you use a relaxer and whether it contains lye. You may want to consider switching to a relaxer that doesn’t contain lye or possibly using a relaxer less frequently.

We know that Black women are underrepresented in clinical trials. Researchers suspect Black women may be uniquely exposed to chemicals in products that contribute to their poorer health outcomes. But without enough Black women enrolled in studies, it’s difficult to figure out exactly what is happening.

Since research suggests that nearly 75% of Black women use some type of chemical relaxer on their hair, Dr. Bertrand believes that more research is needed to better understand any links between breast cancer and hair relaxers.

“Consistent results from several studies are needed before it can be concluded that use of certain hair relaxers impacts breast cancer development,” Dr. Bertrand added.

Read more about the links between chemicals in personal care products and breast cancer risk.

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Written by: Jamie DePolo, senior editor

Reviewed by: Brian Wojciechowski, M.D., medical adviser

References

  1. Boston University. Slone Epidemiology Center. Black Women’s Health Study. Available at: https://www.bu.edu/bwhs/

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