While uterine cancer represents only 3% of all cancer diagnoses in the United States, it remains the most common female reproductive cancer. Also, experts have noted rising rates of uterine cancer mortality in recent years. These statistics promote the need to identify risk factors that could reduce the uterine cancer burden.
To investigate potential risk factors associated with uterine cancer onset, a group of researchers questioned the impact of hair products, such as dyes and straightening chemicals which previous research has linked to breast and ovarian cancers. Their findings, recently published in the Journal of the National Cancer Institute, suggested that women using chemical hair straightening products had a significantly increased risk of developing uterine cancer.
To investigate potential links between hair products and uterine cancer, the researchers followed over 30,000 women enrolled in a prospective cohort known as the Sister Study. The Sister Study recruited women between 2003 and 2009, and all participants had a sister with breast cancer. When enrolling in the study, women participated in an interview and questionnaire which obtained information about hair product use. The data collected included information on hair dye, straighteners, relaxers, and permanents. The researchers followed participants each year after enrollment for updates on their health, including any cancer diagnoses.
The average follow-up time was 10.9 years meaning that the researchers knew of any cancer diagnoses within this time range. In total, 378 uterine cancer diagnoses occurred within the cohort. While most hair products, including dyes, permanents, and body waves, showed no link to uterine cancer, the researchers found that using straightening products was associated with more uterine cancer diagnoses.
The frequency of use of straightening products also contributed to the development of uterine cancer cases. While the researchers found a significant association between hair straightening products and uterine cancer, the overall risk remained small. Specifically, women who never used chemical hair straightening products exhibited a 1.64% risk of developing uterine cancer before age 70. The risk predicted only elevated slightly for women who had ever used a hair straightening product (2.82%) or reported frequent use (greater than four times a year) of hair straightening products (4.05%).
This study is the first evidence of an association between chemical hair straightening products and uterine cancer. While the data appear statistically significant, more investigation is needed to confirm these findings. Further, parsing the specific chemicals found within these hair straightening products could provide more information on the health risks. The authors note that the results reported may also impact racial health disparities as there is a higher prevalence of hair straightening product use among Black women.
Sources: Carcinogenesis (Coogan), Carcinogenesis (White), J Nat Cancer Inst, Environ Health Perspect, NCI News Release