Women who use permanent hair dyes and chemical straighteners could be at increased risk of breast cancer: Study

Those who used chemical straighteners every 5-8 weeks were about 31% more likely to develop breast cancer, while permanent dye use was associated with a 9% higher risk.

                            Women who use permanent hair dyes and chemical straighteners could be at increased risk of breast cancer: Study
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Women who use permanent hair dyes and chemical hair straighteners have a higher risk of developing breast cancer than women who do not use these products. 

The analysis — conducted by researchers at the National Institute of Environmental Health Sciences (NIEHS) — shows that women who used chemical hair straighteners at least every five to eight weeks were about 31% more likely to develop breast cancer, says the team. Overall, straightener use in the 12 months before enrollment in the study was associated with an 18% higher breast cancer risk. 

Women who regularly used permanent hair dye in the year before enrolling in the study were 9% more likely than women who did not use hair dye to develop breast cancer, says the team.

"Many hair products contain endocrine-disrupting compounds and carcinogens potentially relevant to breast cancer. Women, ages 35-74, were enrolled between 2003-09, and had a sister with breast cancer but were breast cancer-free themselves. During follow-up, 2,794 breast cancers were identified. About 55% of participants reported using permanent dye at enrollment. Among all participants, personal straightener use was associated with breast cancer risk, with higher risk associated with increased frequency. Compared to non-use, the hazard ratio for breast cancer was 1.09 for any current permanent dye use. This association did not vary by frequency of use," says the study. 

The findings, published in the International Journal of Cancer, suggest that breast cancer risk increased with more frequent use of these chemical hair products.

"Researchers have been studying the possible link between hair dye and cancer for a long time, but results have been inconsistent. This study is the first to observe a positive association between chemical straighteners and breast cancer in a prospective cohort setting, where women were asked about their use of hair products before a diagnosis of breast cancer," Dr Alexandra White, head of the NIEHS Environment and Cancer Epidemiology Group, told MEA WorldWide (MEAWW). 

Based on the findings, Dr White recommends that women should be informed of the possibility that hair product use may influence breast cancer risk in order to make their own decisions regarding their use of dye and straighteners. 

"These findings suggest that women should consider their use of hair products in light of the fact that the chemicals in hair dye and chemical straighteners may influence their risk of developing breast cancer. However, the overall risk is not large, and chemical hair products are just one of many factors that may influence a woman's chances of getting breast cancer. Healthcare experts could consider sharing this evidence with others to inform their decisions regarding hair product use," Dr White told MEAWW.

The NIEHS is a part of the National Institutes of Health (NIH), US Department of Health & Human Services. The researchers used data from 46,709 women in the Sister Study. 

The NIEHS Sister Study is prospectively examining environmental and familial risk factors for breast cancer and other diseases in a cohort of 50,000 sisters of women who have had breast cancer. Such sisters have about twice the risk of developing breast cancer as other women, say experts.

In the current study, the researchers found that the risk was higher among African-American women. According to the analysis, using permanent dyes every five to eight weeks or more among African-American women was associated with a 60% increased risk of breast cancer as compared with an 8% increased the risk for white women. 

Overall, permanent dye use was associated with 45% higher breast cancer risk in black women, and 7% higher risk in white women.

"In our study, we see a higher breast cancer risk associated with hair dye use, and the effect is stronger in African American women, particularly those who are frequent users," says Dr White.

While the association between straightener use and breast cancer was similar in African American and white women, straightener use was much more common among African American women, say experts. 

The research team found little to no increase in breast cancer risk for semi-permanent or temporary dye use.

Hair-dye use widespread in US

According to NIH's National Cancer Institute, many people in the US and Europe use hair dyes. It has been estimated that more than one-third of women above 18 in the US and about 10% of men over age 40 use some type of hair dye. 

"Modern hair dyes are classified as permanent (or oxidative), semi-permanent, and temporary. Over 5,000 different chemicals are used in hair dye products, some of which are reported to be carcinogenic (cancer-causing) in animals," according to a fact sheet on hair dyes and cancer risks on the National Cancer Institute website. 

It further says, "Early hair dye formulations contained chemicals, including aromatic amines that were found to cause cancer in animals. In the mid- to late 1970s, however, manufacturers changed the components in dye products to eliminate some of these chemicals. It is not known whether some of the chemicals still used in hair dyes can cause cancer. Given the widespread use of hair dye products, even a small increase in risk may have a considerable public health impact." 

Researchers say more studies are needed

Dr Dale Sandler, co-author of the study and chief of the NIEHS epidemiology branch, cautioned that though there is some prior evidence to support the association with chemical straighteners, these results need to be replicated in other studies.

"We are exposed to many things that could potentially contribute to breast cancer, and it is unlikely that any single factor explains a woman's risk. While it is too early to make a firm recommendation, avoiding these chemicals might be one more thing women can do to reduce their risk of breast cancer," says Dr Sandler. 

According to Dr White says since semi-permanent dyes were not associated with breast cancer risk in this study, women might consider switching from permanent to semi-permanent products if those products would work for them. "More research is needed to identify the specific constituents in permanent dye and straighteners that are contributing to a higher risk," Dr White told MEAWW.

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