Takkouche Bahi, Etminan Mahyar, Montes-Martínez Agustín
Department of Preventive Medicine, University of Santiago de Compostela, Santiago de Compostela, Spain.
JAMA. 2005 May 25;293(20):2516-25. doi: 10.1001/jama.293.20.2516.
Use of hair dyes has been suggested recently as a risk factor for several types of cancer in epidemiologic studies. This alarming news and controversial declarations by scientific organizations and general media have made necessary a systematic evaluation of the epidemiologic evidence.
To examine the association between personal use of hair dyes and relative risk of cancer.
We retrieved studies published in any language by systematically searching the MEDLINE (1966-January 2005), EMBASE, LILACS, and ISI Proceedings computerized databases and by manually examining the references of the original articles, reviews, and monographs retrieved.
We included cohort and case-control studies reporting relative risk estimates and 95% confidence intervals (CIs) (or data to calculate them) of personal hair dye use and cancer. We excluded studies that dealt with occupational exposure. We carried out separate analyses for bladder, breast, and hematopoietic cancers and cancers of other sites. Seventy-nine studies were included of 210 articles identified in the search.
Data were extracted independently by 2 investigators. We used a standardized questionnaire to record information on study design, sample size, type of controls, year of publication, adjustment factors, and relative risks of cancer among ever users of hair dyes. When possible, we extracted association measures on use of permanent dyes and extensive use (>200 lifetime episodes of dye use).
Study-specific relative risks were weighted by the inverse of their variance to obtain fixed- and random-effects pooled estimates. The pooled relative risk for ever users of hair dyes was 1.06 (95% CI, 0.95-1.18) for breast cancer (14 studies), 1.01 (95% CI, 0.89-1.14) for bladder cancer (10 studies), and 1.15 (95% CI, 1.05-1.27) for hematopoietic cancers (40 studies). Other cancers were examined by only 1 or 2 studies, of which the pooled or single relative risk was elevated for brain cancer, ovarian cancer, and cancer of the salivary glands. No effect was observed for use of permanent dyes or for extensive use.
We did not find strong evidence of a marked increase in the risk of cancer among personal hair dye users. Some aspects related to hematopoietic cancer and other cancers that have shown evidence of increased risk in 1 or 2 studies should be investigated further.
近期的流行病学研究表明，使用染发剂是多种癌症的风险因素。这一令人担忧的消息以及科学组织和大众媒体的争议性声明使得对流行病学证据进行系统评估成为必要。
研究个人使用染发剂与患癌相对风险之间的关联。
我们通过系统检索MEDLINE（1966年 - 2005年1月）、EMBASE、LILACS和ISI Proceedings计算机数据库，并人工查阅检索到的原始文章、综述和专著的参考文献，检索了以任何语言发表的研究。
我们纳入了报告个人染发剂使用与癌症相对风险估计值及95%置信区间（CI）（或计算它们的数据）的队列研究和病例对照研究。我们排除了涉及职业暴露的研究。我们分别对膀胱癌、乳腺癌、造血系统癌症以及其他部位的癌症进行了分析。在检索到的210篇文章中，纳入了79项研究。
由2名研究人员独立提取数据。我们使用标准化问卷记录关于研究设计、样本量、对照类型、发表年份、调整因素以及染发剂使用者患癌相对风险的信息。如有可能，我们提取了关于使用永久性染发剂和大量使用（一生中染发超过200次）的关联测量值。
根据研究特异性相对风险的方差倒数进行加权，以获得固定效应和随机效应合并估计值。染发剂使用者患乳腺癌（14项研究）的合并相对风险为1.06（95%CI，0.95 - 1.18），患膀胱癌（10项研究）的合并相对风险为1.01（95%CI，0.89 - 1.14），患造血系统癌症（40项研究）的合并相对风险为1.15（95%CI，1.05 - 1.27）。其他癌症仅由1或2项研究进行了检查，其中脑癌、卵巢癌和唾液腺癌的合并或单一相对风险有所升高。未观察到使用永久性染发剂或大量使用有任何影响。
我们没有找到有力证据表明个人染发剂使用者患癌风险显著增加。与造血系统癌症和其他癌症相关的一些方面，在1或2项研究中显示出风险增加的证据，应进一步调查。
