Hair straightening products may increase the risk of uterine cancer
Women who use chemical hair straighteners may be at greater risk uterine cancer but women who don’t, according to a major new study from the National Institutes of Health (NIH).
Study participants who reported frequent use of hair straightening products, defined as more than four times in the previous year, were more than twice as likely to develop uterine cancer as those who did not use the products. The the findings were published on October 17 in Journal of the National Cancer Institute.
“This rate of doubling is concerning,” said the lead author, Dr. Alexandra Whitechief of the NIEHS Environmental and Cancer Epidemiology Group in Research Triangle Park, North Carolina, d Media Release. “It is important to put this information in context – uterine cancer is relatively rare a type of cancer.”
Unlike many other cancers, the rate of uterine cancer is increasing in the US
Uterine cancer occurs when malignant (cancerous) cells form in the tissues of the endometrium, which is the lining of the uterus. It accounts for about 3 percent of all new cancer cases, according to the data National Cancer Institutebut it is the most common cancer of the female reproductive system, with 65,950 estimated new cases in 2022.
Unlike many cancers, the incidence and mortality rates of uterine cancer are increasing. The number of new cases is increasing by 0.6 percent annually from 2010 to 2019, and death rates increased by an average of 1.7 percent annually over the same time period.
Previous research has linked some types of hair products to breast and ovarian cancer
Certain hair products, such as straighteners and some dyes, have been linked to hormone-sensitive cancers, including breast and ovarian cancer, according to the authors. Previous research has found a link between the use of straighteners and a higher incidence of ovarian cancer, but this is the first study to examine how the products may affect the risk of uterine cancer.
Women who frequently used hair straightening products were at higher risk of uterine cancer
33,497 participants took part in the trial sister study, cohort that included women aged 35 to 74 who were free of breast cancer when the study began and had at least one sibling diagnosed with breast cancer.
The average age of the participants was 58 years; 85.6 percent were white, 7.4 percent were black, and 4.4 percent were Hispanic.
At the start of the study, all women completed an interview and questionnaire that included questions about the use of various hair products such as straighteners, relaxers, and permanent and semi-permanent hair dyes.
The women were followed for almost 11 years, during which time 378 cases of uterine cancer were diagnosed.
The researchers found that women who reported frequent use of hair straightening products, defined as more than four times in the previous year, were more than twice as likely to develop uterine cancer as those who did not use the products.
“We estimated that 1.64 percent of women who have never used hair straighteners will develop uterine cancer by the age of 70, but for frequent users, that risk rises to 4.05 percent,” said Dr. White.
The overall risk of uterine cancer is still low
The Sister Study is a large, well-designed cohort study, and the authors conducted a rigorous analysis to test this association, says Ashley Felix, PhD, MPH, researcher who studies uterine cancer and health care disparities at the Ohio State University Comprehensive Cancer Center in Columbus, but was not involved in the new study. “These findings should definitely be communicated to consumers,” she adds.
“Although no previous study has specifically assessed the relationship between hair straightener use and uterine cancer, these findings parallel other analyzes examining the association between hair straightener use and breast and ovarian cancer risk, providing biological plausibility,” said Dr. Felix.
According to the authors, this does not mean a large absolute increase in risk, she notes. “So even though the risk has doubled, the absolute risk of developing uterine cancer in either group is still low. This is because uterine cancer is a relatively rare cancer,” she says.
Hair dyes, bleaches, highlights, or perms were not associated with a higher risk of uterine cancer
The researchers found no association with uterine cancer for other hair products the women reported using, including hair dyes, bleaches, highlights or perms.
The researchers did not collect information about the brands or ingredients in the hair products the women used. But several chemicals found in straighteners (such as parabens, bisphenol A, metals, and formaldehyde) can contribute to uterine enlargement. cancer risk observed, the authors wrote.
Researchers believe that exposure to chemicals from the use of hair products, especially straighteners, may be of greater concern than other personal care products due to increased absorption through the scalp, which may be exacerbated by burns and lesions caused by flat irons.
Black women may be at greater risk due to frequency of use
Approximately 60 percent of participants who reported using hair straighteners in the previous year identified as black women. Although the study did not find that the relationship between straightener use and the incidence of uterine cancer differed by race, the adverse health effects may be greater in black women.
“Because black women are more likely to use hair straightening or relaxer products and tend to begin use at an earlier age than other racial and ethnic groups, these findings may be even more relevant to them,” said Dr. Che-Jung Chang, author of the new study and researcher in the NIEHS Epidemiology Branch, in ed.
Black women are at higher risk of uterine cancer
Black women in particular have a higher risk of developing aggressive subtypes of endometrial cancer (called Type II in the study), and recent data show that the risk of developing less aggressive subtypes also increases among black women compared to white women, Felix says.
U study published May 22, 2019 by the NIHresearchers found that aggressive, non-endometrial subtypes of uterine cancer are increasing dramatically in all racial or ethnic groups, and are increasing at a much higher rate in black women than in all other racial or ethnic groups.
“Unfortunately, the study was not able to examine the relationship between the use of hair straighteners and the risk of (aggressive) type II uterine cancer due to small numbers. If we were to see a strong association with the use of hair straighteners and the risk of type II uterine cancer, it might suggest one pathway by which black women are more likely than white women to develop these aggressive tumors, given their higher prevalence of use.” says Felix. Because of this limitation, the findings do not improve our understanding of the known treatment differences that exist for uterine cancer, she adds.
Should women be warned about using hair straighteners?
Because this is the only study looking at the association between the use of hair straighteners and the risk of uterine cancer, we would like to see these results in independent studies to have stronger evidence of an association, says Felix.
“Nonetheless, the results of this study along with the sparse studies done for breast and ovarian cancer suggest that something is going on with regard to the use of hair straighteners and the risk of certain cancers. “I think women should know about these associations, but in terms of ‘warning’ women, the evidence is still in its infancy,” she says.
White said, “More research is needed to confirm these findings in different populations, to determine whether hair products contribute to health disparities in uterine cancer, and to identify specific chemicals that may increase women’s cancer risk.”
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