Women who use permanent hair dye products to colour their hair at home do not experience greater risk of most cancers or greater cancer related mortality, finds a large US prospective cohort study. While this should provide general reassurance to users of permanent hair dyes, the authors say they did find a slight increase in risk of ovarian cancer and some cancers of the breast and skin. Natural hair colour was also found to impact on the likelihood of some cancers.
Use of hair dye is very popular, particularly among older age groups keen to cover up signs of grey. For example, it is estimated that it is used by 50-80% of women and 10% of men aged 40 and older in the US and Europe. The most aggressive hair dyes are the permanent types and these account for approximately 80% of hair dyes used in the US and Europe, and an even greater proportion in Asia.
While the World Health Organisation's International Agency for Research on Cancer has classified occupational exposure to hair dyes as a probable carcinogen, there is no warning about personal use because existing evidence is inconclusive.
To gain a better understanding of the risk of cancer from use of personal hair dye, researchers analysed data on 117,200 women from the Nurses' Health Study, based at Brigham and Women's Hospital, Boston.
The women did not have cancer at the start of the study and were followed for 36 years.
The results showed no increased risk of most cancers or of cancer death in women who reported having ever used permanent hair dyes compared with those who had never used such dyes.
Use of hair dye did not increase risk of cancers of the bladder, brain, colon, kidney, lung, blood and immune system, or most cancers of the skin (cutaneous squamous cell carcinoma and melanoma) or breast (oestrogen receptor positive, progesterone receptor positive or hormone receptor positive).
Ever use of permanent dyes was associated with a slightly increased risk of the basal cell carcinoma of the skin, and this risk was higher in women with naturally light hair.
An increased risk of three types of breast cancer – oestrogen receptor negative, progesterone receptor negative, and hormone receptor negative – and ovarian cancer was also linked to use of permanent dyes, with risk rising according to the cumulative amount of dye women were exposed to. An increased risk of Hodgkin lymphoma was also seen with use of permanent hair dye but only for women with naturally dark hair.
"Possible explanations could be that shades of permanent hair dyes are associated with the concentration of ingredients, with darker colours having higher concentrations," the authors say.
This is an observational study, so can't establish cause. The authors also point to some limitations, including the lack of racial diversity of study participants, which mainly included white US women with European ancestry, and the possibility that other unmeasured factors, such as use of other products, may have affected the results.
What's more, assessments of exposure to hair dye stopped relatively early in the follow-up period so some women may have started, stopped or changed their hair dye after this time, and some users of non-permanent hair dyes might have misclassified themselves as permanent hair dye users.
Nevertheless, the authors say their findings "offer some reassurance against concerns that personal use of permanent hair dyes might be associated with increased cancer risk or mortality."
However, they add that the positive associations for some cancers with different hair colour types warrant further investigation.
Objective: To evaluate the associations between personal use of permanent hair dyes and cancer risk and mortality.
Design: Prospective cohort study.
Setting and participants: 117 200 women enrolled in the Nurses’ Health Study, an ongoing prospective cohort study of female nurses in the United States. The women were free of cancer at baseline, reported information on personal use of permanent hair dyes, and were followed for 36 years.
Exposure: Status, duration, frequency, and integral use (cumulative dose calculated from duration and frequency) of permanent hair dyes. Age at first use and time since first use of permanent hair dyes.
Main outcome measures: Associations of personal use of permanent hair dyes with risk of overall cancer and specific cancers, and cancer related death. Age and multivariable adjusted hazard ratios and 95% confidence intervals were estimated by using Cox proportional hazard models.
Results: Ever users of permanent hair dyes had no significant increases in risk of solid cancers (n=20 805, excluding non-melanoma skin cancers; hazard ratio 0.98, 95% confidence interval 0.96 to 1.01) or hematopoietic cancers overall (n=1807; 1.00, 0.91 to 1.10) compared with non-users. Additionally, ever users did not have an increased risk of most specific cancers (cutaneous squamous cell carcinoma, bladder cancer, melanoma, estrogen receptor positive breast cancer, progesterone receptor positive breast cancer, hormone receptor positive breast cancer, brain cancer, colorectal cancer, kidney cancer, lung cancer, and most of the major subclasses and histological subtypes of hematopoietic cancer) or cancer related death (n=4860; 0.96, 0.91 to 1.02). Basal cell carcinoma risk was slightly increased for ever users (n=22 560; 1.05, 1.02 to 1.08). Cumulative dose was positively associated with risk of estrogen receptor negative breast cancer, progesterone receptor negative breast cancer, hormone receptor negative breast cancer, and ovarian cancer. An increased risk of Hodgkin lymphoma was observed only for women with naturally dark hair (based on 70 women, 24 with dark hair), and a higher risk of basal cell carcinoma was observed for women with naturally light hair.
Conclusion: No positive association was found between personal use of permanent hair dye and risk of most cancers and cancer related mortality. The increased risk of basal cell carcinoma, breast cancer (estrogen receptor negative, progesterone receptor negative, hormone receptor negative) and ovarian cancer, and the mixed findings in analyses stratified by natural hair color warrant further investigation.
Yin Zhang, Brenda M Birmann, Jiali Han, Edward L Giovannucci, Frank E Speizer, Meir J Stampfer, Bernard A Rosner, Eva S Schernhammer
[link url="https://www.sciencedaily.com/releases/2020/09/200902185459.htm"]BMJ material[/link]
[link url="https://www.bmj.com/content/370/bmj.m2942"]BMJ abstract[/link]