Personal Use of Hair Dyes and the Risk of Bladder Cancer: Results of a Meta-Analysis

Abstract

SYNOPSISObjective. This study examined the methodology of observational studies that explored an association between personal use of hair dye products and the risk of bladder cancer.Methods. Data were pooled from epidemiological studies using a general variancebased meta-analytic method that employed confidence intervals. The outcome of interest was a summary relative risk (RRs) reflecting the risk of bladder cancer development associated with use of hair dye products vs. non-use. Sensitivity analyses were performed to explain any observed statistical heterogeneity and to explore the influence of specific study characteristics of the summary estimate of effect.Results. Initially combining homogenous data from six case-control and one cohort study yielded a non-significant RR of 1.01 (0.92, 1.11), suggesting no association between hair dye use and bladder cancer development. Sensitivity analyses examining the influence of hair dye type, color, and study design on this suspected association showed that uncontrolled confounding and design limitations contributed to a spurious non-significant summary RR. The sensitivity analyses yielded statistically significant RRs ranging from 1.22 (1.11, 1.51) to 1.50 (1.30, 1.98), indicating that personal use of hair dye products increases bladder cancer risk by 22% to 50% vs. non-use.Conclusion. The available epidemiological data suggest an association between personal use of hair dye products and increased risk of bladder cancer.

Personal use of hair dyes and risk of bladder cancer: a meta-analysis of epidemiologic data

“…Results for bladder cancer risk from studies of occupationally exposed populations, such as barbers or hairdressers, are inconsistent with no associations or weak associations reported in some studies [2,7,8], and positive associations reported in other studies [9]. Recently, the possible association of personal hair dye use with bladder cancer has been examined in two published meta-analyses by Huncharek and Kupelnick [10] and Takkouche et al [11]. Although these publications reviewed nearly the same set of studies, the conclusions of the authors differed with respect to the potential risk of bladder cancer and personal hair dye use.…”

Personal Permanent Hair Dye Use Is Not Associated with Bladder Cancer Risk: Evidence from a Case-Control Study

“…Two recent metaanalyses yielded contradictory conclusions, one found a pooled relative risk of 1.01 (95% CI, 0.89-1.14; ref. 5) and the other concluded that there was a 22% to 50% increased bladder cancer risk for permanent hair dye users (6). However, the latter report did not include the most recent negative casecontrol study (10) and the pooled significant ORs were obtained by excluding selected studies that the authors deemed questionable in study design.…”

“…The fact that almost any hair dye on the market contains small amounts of aromatic amines and that aromatic amines are carcinogenic in animals (2, 3) has generated great interest in studying the association between hair dye use and cancer risk, especially bladder cancer risk. Although occupational exposure to hair dyes by hairdressers and barbers has been shown to increase bladder cancer risk in a number of epidemiologic studies (4), whether or not personal hair dye use may increase bladder cancer risk remains controversial with fewer studies published and fewer cases and exposed individuals (4)(5)(6). In this study, we used one of the largest bladder cancer case-control studies to evaluate the association between personal hair dye use and bladder cancer risk.…”

Hair dye use and risk of human cancer

“…Another population-based case-control study involving 897 cases and equal number of controls found a two-fold increased risk of bladder cancer among women who had used permanent hair dyes at least once a month, and the risk increased to 3.3-fold (95% CI: 1.3,8.4) for women who were regular (at least monthly) users for at least 15 years (15). The cohort studies generally reported no association between bladder cancer and hair dye use (16)(17)(18)(19)(20) Three meta-analysis studies have been published since 2005 assessing risk of bladder cancer and exposure to hair dyes (21)(22)(23). A study by Huncharek and Kupelnick (21), which had significant exclusion criteria (which limited the meta-analysis to a mere seven studies) and a unique weighted method of analyzing the data, suggested that there is a relative risk between 1.22 (95% CI: 1.11, 1.51) and 1.50 (95% CI: 1.30, 1.98).…”

“…The cohort studies generally reported no association between bladder cancer and hair dye use (16)(17)(18)(19)(20) Three meta-analysis studies have been published since 2005 assessing risk of bladder cancer and exposure to hair dyes (21)(22)(23). A study by Huncharek and Kupelnick (21), which had significant exclusion criteria (which limited the meta-analysis to a mere seven studies) and a unique weighted method of analyzing the data, suggested that there is a relative risk between 1.22 (95% CI: 1.11, 1.51) and 1.50 (95% CI: 1.30, 1.98). Another two meta-analysis studies by Takkouche et al (22) and Kelsh et al (23) found no association between bladder cancer and hair dye use.…”