NEW YORK (Reuters Health) - Women who use chemical relaxers to straighten their hair do not seem to be at increased risk of breast cancer, according to a new study.
There's no evidence that the major ingredients in hair relaxers -- such as lye and calcium hydroxide -- promote cancer. However, manufacturers need not list all of the ingredients they use in cosmetics (as some are considered trade secrets), and it's not clear whether some of these substances might be harmful.
Because many African-American women regularly use hair relaxers, often throughout their lives, it's important to know whether the products carry any long-term health risks, researchers say.
The new study found that among more than 48,000 African-American women, those who used hair relaxers most frequently were no more likely to develop breast cancer than those who rarely used the products.
"Our study provides reassurance that hair relaxers in general are not increasing the incidence of breast cancer," Dr. Lynn Rosenberg, the study's lead author, told Reuters Health.
That said, "nothing is 100-percent certain," noted Rosenberg, who is associate director of the Slone Epidemiology Center at Boston University, Massachusetts.
The study did not look at individual products, she explained, and it's still possible that some contain harmful substances. For now, however, there's "very little evidence" that women who use hair relaxers should worry that they're raising their odds of breast cancer, according to Rosenberg.
She and her colleagues report their findings in the journal Cancer Epidemiology, Biomarkers & Prevention.
The researchers based their results on data from the Black Women's Health Study, which began following a large group of African American women from across the U.S. in 1995. Study participants completed questionnaires on their health and lifestyle habits every two years.
Of 48,167 women who reported on their hair relaxer use, 574 had developed breast cancer by 2003. Women who used hair relaxers most frequently -- seven or more times per year -- were no more likely to develop breast cancer than their peers who rarely or never used the products.
The same was true when the researchers compared non-users to women who'd used hair relaxers for 20 years or more.
Compared with white women, African-American women are more likely to develop breast cancer before the age of 45, for reasons that aren't completely clear. In this study, Rosenberg pointed out, there was no evidence that hair relaxers increased breast cancer risk in older or younger women.
SOURCE: Cancer Epidemiology, Biomarkers & Prevention, May 2007.
Because African American women use hair relaxers more regularly than white women, and because African American women are more likely to develop breast cancer before age 45 than white women, researchers wanted to know if breast cancer was diagnosed more often in the women who used hair relaxers. The answer was no.
The researchers were confident about the results because the study involved a large number of women (more than 48,000) and followed them for about 8 years. Some of the women in the study used hair relaxers 7 or more times per year, and some women used relaxers for more than 20 years.
Researchers are trying to figure out why African American women are more likely to develop breast cancer at a younger age than white women. It's possible that this difference is due to many factors, including:
Understanding the differences in the way breast cancer acts in different groups of women is one way that researchers can discover clues to the causes of breast cancer and may help develop new treatments.
We know that family history, genetics, diet, and lifestyle factors can influence a woman’s breast cancer risk. To learn more about risk and steps you can take to reduce your breast cancer risk, visit the breastcancer.org Lower Your Risk section.
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