Hair coloring products are known to contain several chemical compounds including aromatic amines which have been found to be mutagenic and carcinogenic in several experimental studies (10
). The parallel analysis of NHL found an increased risk among women who used hair dyes before 1980 and for those who use dark permanent dyes for 25 years or more (13
). This population-based case-control study showed no association between use of hair coloring products and risk of multiple myeloma. Our study is consistent with null associations reported in three case-control studies (7
) and two cohort studies (6
). Two case-control studies and one cohort study, however, have reported hair color use as a risk factor for myeloma especially among those reporting use of dark hair dyes for long periods of time (5
); we did not observe this association here. Only one case-control study evaluated the product type (9
), only two studies examined the frequency of use (5
), and several of these previous reports are based on smaller numbers than those presented here.
Several strengths and potential limitations of the study design should be considered in interpreting our null findings. In this study, we collected lifetime histories of hair coloring product use with detailed questions on type, shade, duration of use, age at first use, and number of applications. This allowed us to calculate risk for various levels and categories of exposure, including time period of use. As with previous studies, our ability to evaluate hair dye use and myeloma risk was limited by a small sample size (# exposed: cases = 116; controls = 500) that prevented us from fully evaluating hair dye use and any subsequent risk overall and within well-known high risk groups, such as blacks and dark permanent dye users. The differing participation rates between cases and controls and potential selection bias due to low response rates is also a concern. Although no information was available on the characteristics of non-participants, we used vital statistics data to compare the demographic profile of participating controls with that of the Connecticut population from which they were drawn. In terms of demographic characteristics controls were similar to the general population (17
). Therefore, it seems unlikely that controls were misrepresented in our study regarding exposure-related characteristics.
In summary, we did not find any evidence of an association between hair coloring product use and myeloma risk. However, given the conflicting body of literature on hair coloring product use and risk of multiple myeloma, this question should be further evaluated in larger studies or consortia, using well characterized hair dye information and particularly among high risk groups.
- We did not find any association between ever reporting hair coloring product use and myeloma risk among all users, users of semi-permanent products, permanent products, or dark permanent products.
- There were no significant associations among women who used hair dyes before 30 years of age, who started use before 1980, who had ≥240 lifetime applications, or for dark permanent users with 28 or more years of use.
- Multiple myeloma is a deadly disease but few risk factors have been identified. Further evaluation of hair dye constituents is warranted in relation to this and other cancers types among large subsets of study subjects so that we can rule out any deleterious consequences on human health.