Personal Use of Hair Dye and the Risk of Certain Subtypes of Non-Hodgkin Lymphoma

Yawei Zhang; Silvia De Sanjose; Paige M. Bracci; Lindsay M. Morton; Rong Wang; Paul Brennan; Patricia Hartge; Paolo Boffetta; Nikolaus Becker; Marc Maynadie; Lenka Foretova; Pierluigi Cocco; Anthony Staines; Theodore Holford; Elizabeth A. Holly; Alexandra Nieters; Yolanda Benavente; Leslie Bernstein; Shelia Hoar Zahm; Tongzhang Zheng

Disclosures

Am J Epidemiol. 2008;167(11):1321-1331. 

In This Article

Results

Table 2 provides demographic and subtype data for the pooled study population by case (n = 4,461) or control (n = 5,799) status. Both the case population and the control population were predominantly White (≥92 percent), and they had similar age and sex distributions.

Table 3 presents the results for personal hair-dye use and NHL risk, overall and by sex and time period of hair-dye use. Among women, 75 percent of the cases and 70 percent of the controls reported ever having used hair dyes. Stratification by time period of use showed an increased risk of NHL among women who started using hair dyes before 1980 as compared with nonusers (odds ratio (OR) = 1.3, 95 percent confidence interval (CI): 1.1, 1.4). The increased risk among women did not show a clear pattern by product type or color. For women who started using hair dyes in 1980 or later, an increased risk was associated with use of nonpermanent dark-colored dye (OR = 1.3, 95 percent CI: 1.0, 1.6). Among men, approximately 10 percent of cases and 10 percent of controls had ever used hair dyes. Risk of NHL was not associated with hair-dye use before or after 1980 among men. Thus, the results presented below are restricted to women.

Use of hair dye was associated with increased risks of follicular lymphoma and CLL/SLL but not of other NHL subtypes ( table 4 ). The increased risk of follicular lymphoma was not modified or confounded by time period of use. However, for women who started using hair dyes in 1980 or later, risk of follicular lymphoma was increased among those who had used dark-colored dyes (for permanent dark-colored dyes, OR = 1.5, 95 percent CI: 1.1, 2.1; for nonpermanent dark-colored dyes, OR = 1.7, 95 percent CI: 1.1, 2.4). An increased risk of CLL/SLL was limited to women who started using hair dyes before 1980 (OR = 1.5, 95 percent CI: 1.1, 2.0). The risk did not vary by product type or color. Risk of other B-cell or T-cell lymphomas was not associated with hair-dye use. Risk estimates from random-effects models were consistent with the results from dichotomous or polytomous unconditional logistic regression models (figure 1). However, risk estimates from random-effects models were less precise.

Figure 1.

Odds ratios (ORs) for non-Hodgkin lymphoma (NHL) among women, by study center, in a pooled analysis of hair-dye use and NHL, 1988-2003. Boxes show results from individual studies; diamonds indicate pooled data. Bars, 95% confidence interval (CI). EpiLymph, International Case-Control Study of Lymphomas from Europe; NCI, NCI/SEER (National Cancer Institute/Surveillance, Epidemiology, and End Results) Multi-Center Case-Control Study; UCSF, Epidemiology of NHL Study (University of California, San Francisco); Yale, Connecticut Women's NHL Study (Yale University).

Results from further detailed analyses of the associations of hair-dye use with follicular lymphoma and CLL/SLL among women are presented in table 5 . Overall, a longer duration of hair-dye use was associated with a greater risk of follicular lymphoma (p-trend = 0.01), and the significant trend was mainly seen in women who started using the products before 1980 (p-trend < 0.01). For women who started using hair dyes in 1980 or afterward, significant trends for duration of use were observed only for permanent (p-trend = 0.02) and dark-colored (p-trend = 0.04) dyes. An increased risk of CLL/SLL was mainly observed among women who started using hair dyes before 1980. The risk was increased with greater duration, frequency, and total number of applications (p values for trend were 0.02, <0.01, and <0.01, respectively). However, no significant trends were observed among hair-dye users only. No major differences in risk patterns were observed for different types and colors of hair dye by frequency of application or total number of applications (data not shown).

Stratification by continent among persons who started using hair dyes before 1980 showed an increased risk of CLL/SLL associated with hair-dye use for European women (OR = 2.2, 95 percent CI: 1.4, 3.4) but not for US women (OR = 1.1, 95 percent CI: 0.8, 1.7). The association with follicular lymphoma, however, was apparent for both European women (OR = 1.4, 95 percent CI: 1.0, 1.8) and US women (OR = 1.6, 95 percent CI: 1.0, 2.7).

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