Does Hair Dye Use Increase the Risk of Breast Cancer? A Population-Based Case-Control Study of Finnish Women.
BACKGROUND
Role of hair dyes in the etiology of breast cancer has occasionally raised concern but previous research has concluded with mixed results. Remnants of prohibited aromatic amines have been found in many hair dye products, and elevated levels of DNA-adducts of these amines have been detected from breast epithelial cells of hair dye users. However, the IARC working group has concluded that there is inadequate evidence for carcinogenicity of personal hair dye use and limited evidence in experimental animals for carcinogenicity of hair colorants.


METHODS
We investigated whether the use of hair dyes is associated with breast cancer risk in women. The study design was a retrospective population-based case-control study in Finland, with a self-administered questionnaire from 6,567 breast cancer patients, aged 22-60 years and diagnosed in 2000-2007, and their 21,598 matched controls. We report odds ratios (OR) with 95% confidence interval (95% CI) from a conditional logistic regression model applied to the frequency matched sets of cases and controls. Bias-adjusted odds ratios from the sensitivity analysis are also presented.


RESULTS
After adjusting for potential confounders, the odds of breast cancer increased by 23% (OR: 1.23, 95% CI: 1.11-1.36) among women who used hair dyes compared to those who did not. In women born before 1950 an increase of 28% was noted (OR: 1.28, 95% CI: 1.10-1.48). We also observed a significant trend between the OR and cumulative use of hair dyes (P: 0.005). Bias-adjusted odds ratios varied between 1.04 and 2.50.


CONCLUSIONS
Our results suggest that use of hair dyes is associated with breast cancer incidence. The impact on public health may be substantial due to vast popularity of hair coloring in modern societies. It should be noted that regardless of all efforts, a possibility of bias cannot definitively be ruled out and use of a prospective design is warranted. Based on the present results, it may be concluded however that safety of hair dyes in relation to breast cancer cannot yet be fully acknowledged and lack of external safety assessment within the cosmetics industry is of major concern.
Finnish Cancer Registry, Institute for Statistical and Epidemiological Cancer Research, Unioninkatu 22, FI-00130, Helsinki, Finland.
Sanna
S
Heikkinen
Finnish Cancer Registry, Institute for Statistical and Epidemiological Cancer Research, Unioninkatu 22, FI-00130, Helsinki, Finland; University of Helsinki, Hjelt Institute, Department of Public Health, PO Box 41 (Mannerheimintie 172), FI-00014 University of Helsinki, Helsinki, Finland.
Janne
J
Pitkäniemi
Finnish Cancer Registry, Institute for Statistical and Epidemiological Cancer Research, Unioninkatu 22, FI-00130, Helsinki, Finland.
Tytti
T
Sarkeala
Finnish Cancer Registry, Institute for Statistical and Epidemiological Cancer Research, Unioninkatu 22, FI-00130, Helsinki, Finland; School of Health Sciences, University of Tampere, FI-33014 University of Tampere, Tampere, Finland.
Nea
N
Malila
University of Helsinki, Hjelt Institute, Department of Public Health, PO Box 41 (Mannerheimintie 172), FI-00014 University of Helsinki, Helsinki, Finland.
Markku
M
Koskenvuo
D000328:Adult; D000368:Aged; D001943:Breast Neoplasms / Q000453:epidemiology* / Q000209:etiology*; D016022:Case-Control Studies; D005260:Female; D005387:Finland / Q000453:epidemiology; D006202:Hair Dyes / Q000009:adverse effects*; D006801:Humans; D008875:Middle Aged; D016017:Odds Ratio; D011159:Population Surveillance; D012189:Retrospective Studies; D012307:Risk Factors; D011795:Surveys and Questionnaires
D006202:Hair Dyes