Division of Cancer Epidemiology and Genetics, National Cancer Institute, Bethesda, MD, USA.
Usher Institute of Population Health Sciences and Informatics, Edinburgh Cancer Research Centre, Edinburgh, Scotland.
Carcinogenesis. 2018 Apr 5;39(4):571-579. doi: 10.1093/carcin/bgy002.
Skin lighteners and hair relaxers, both common among women of African descent, have been suggested as possibly affecting breast cancer risk. In Accra and Kumasi, Ghana, we collected detailed information on usage patterns of both exposures among 1131 invasive breast cancer cases and 2106 population controls. Multivariate analyses estimated odds ratios (ORs) and 95% confidence intervals (CIs) after adjustment for breast cancer risk factors. Control usage was 25.8% for ever use of skin lighteners and 90.0% for use of hair relaxers for >1 year. The OR for skin lighteners was 1.10 (95% CI 0.93-1.32), with higher risks for former (1.21, 0.98-1.50) than current (0.96, 0.74-1.24) users. No significant dose-response relations were seen by duration, age at first use or frequency of use. In contrast, an OR of 1.58 (95% CI 1.15-2.18) was associated with use of hair relaxers, with higher risks for former (2.22, 1.56-3.16) than current (1.39, 1.00-1.93) users. Although numbers of burns were inconsistently related to risk, associations increased with duration of use, restricted to women who predominately used non-lye products (P for trend < 0.01). This was most pronounced among women with few children and those with smaller tumors, suggesting a possible role for other unmeasured lifestyle factors. This study does not implicate a substantial role for skin lighteners as breast cancer risk factors, but the findings regarding hair relaxers were less reassuring. The effects of skin lighteners and hair relaxers on breast cancer should continue to be monitored, especially given some biologic plausibility for their affecting risk.
皮肤美白剂和头发拉直剂在非裔女性中很常见，有人认为它们可能会影响乳腺癌的风险。我们在加纳的阿克拉和库马西收集了 1131 例浸润性乳腺癌病例和 2106 名对照人群中这两种暴露的详细使用模式信息。多变量分析在调整乳腺癌危险因素后估计了比值比（OR）和 95％置信区间（CI）。控制组的使用率为，曾经使用过皮肤美白剂的占 25.8％，使用头发拉直剂超过 1 年的占 90.0％。皮肤美白剂的 OR 为 1.10（95％CI 0.93-1.32），前使用者（1.21，0.98-1.50）的风险高于当前使用者（0.96，0.74-1.24）。按使用持续时间、首次使用年龄或使用频率均未观察到显著的剂量-反应关系。相比之下，使用头发拉直剂的 OR 为 1.58（95％CI 1.15-2.18），前使用者（2.22，1.56-3.16）的风险高于当前使用者（1.39，1.00-1.93）。尽管烧伤次数与风险的关系不一致，但与使用持续时间有关，仅限于主要使用非碱产品的女性（P 趋势<0.01）。这种情况在孩子较少和肿瘤较小的女性中最为明显，表明可能存在其他未测量的生活方式因素。本研究并未表明皮肤美白剂是乳腺癌的重要危险因素，但关于头发拉直剂的发现则不那么令人放心。应继续监测皮肤美白剂和头发拉直剂对乳腺癌的影响，特别是考虑到它们对风险的影响具有一定的生物学合理性。
