Abstract 3392: Personal use of permanent hair dyes and cancer risk and mortality in US women: Prospective cohort study
Authors: Zhang Yin , Birmann Brenda , Han Jiali , Giovannucci Edward , Speizer Frank , Stampfer Meir , Rosner Bernard , Schernhammer Eva 
Published: September 2020

Abstract
Background Personal use of permanent hair dyes has been discussed and examined as a potential risk factor for a variety of cancers. Epidemiological evidence regarding the relationship between personal use of permanent hair dyes and cancer risk and mortality remains inconclusive.
Methods The Nurses' Health Study is an ongoing prospective cohort study of US female nurses. A total of 117200 women free of cancer at baseline and who reported information on personal use of permanent hair dyes (1976-1982), were included in this analysis and followed for 36 years (1976-2012). Age- and multivariable-adjusted hazard ratios (HRs) and 95% confidence intervals (95%CIs) for associations of personal use of permanent hair dyes with risk of overall and specific cancers and cancer-specific death were estimated by using Cox proportional hazard models. The exposures included status, duration, frequency, and integral use (cumulative dose, calculated based on both duration and frequency) of permanent hair dyes, age at first use and time since first use of permanent hair dyes.
Results There were 20805 overall solid cancer cases (not including major non-melanoma skin cancers), 1807 overall hematopoietic cancer cases, 22560 basal cell carcinoma cases, 2792 cutaneous squamous cell carcinoma cases and 4860 cancer-specific deaths documented during follow-up. Compared with women who never used permanent hair dyes, there was no significant association between ever-users and overall solid cancer risk (not including major non-melanoma skin cancers) (HR =0.98, 95%CI, 0.96-1.01), overall hematopoietic cancer risk (HR =1.00, 95%CI, 0.91-1.10), risk of most specific cancers, and cancer-specific death (HR=0.96, 95%CI, 0.91-1.02). A slightly increased risk of basal cell carcinoma was observed among ever-users. Larger cumulative dose was associated with higher risk of basal cell carcinoma, breast cancer and ovarian cancer. Mixed findings were observed for never/ever use and cumulative dose of permanent hair dyes in analyses stratified by natural hair color for some endpoints. Increased risk of Hodgkin lymphoma (based on very limited cases) was observed only among women with naturally dark hair who dyed their hair presumably using dark-colored permanent hair dyes. Higher risks of basal cell carcinoma and breast cancer were observed specifically among women with naturally light hair.
Conclusion There was no positive association between personal use of permanent hair dyes and risk of most cancers and cancer-specific mortality, except for basal cell carcinoma, breast cancer and ovarian cancer. There were mixed findings for some endpoints (Hodgkin lymphoma, basal cell carcinoma and breast cancer) in analyses stratified by hair color. Further research is needed to confirm current findings.
Citation Format: Yin Zhang, Brenda Birmann, Jiali Han, Edward Giovannucci, Frank Speizer, Meir Stampfer, Bernard Rosner, Eva Schernhammer. Personal use of permanent hair dyes and cancer risk and mortality in US women: Prospective cohort study [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 3392.