Department of Biostatistics and Epidemiology, Graduate School of Public Health, University of Puerto Rico, San Juan, Puerto Rico.
Nutrition and Dietetics Program, Río Piedras Campus, University of Puerto Rico, San Juan, Puerto Rico.
Cancer Epidemiol Biomarkers Prev. 2022 Feb;31(2):430-435. doi: 10.1158/1055-9965.EPI-21-0932. Epub 2021 Nov 22.
Though inconsistent, there is evidence that sun exposure is associated with reduced breast cancer risk. Previous studies have been conducted in geographical regions with seasonal variation in UV radiation, including periods of low to no exposure, and among participants mostly of European descent. Puerto Rico has no significant seasonal fluctuation, with continuous exposure to very high UV radiation.
We conducted a population-based case-control study of breast cancer among women in metropolitan San Juan, Puerto Rico, examining a cumulative sun exposure index (SEI) based on a comparison of reflectance of sun-exposed and non-exposed skin. A chromameter was used to measure skin reflectance and estimate the difference between constitutive (unexposed) and facultative (exposed) skin pigmentation in 307 cases and 328 controls. Breast cancer risk factors were ascertained with interviewer-administered questionnaires. OR and 95% confidence intervals (CI) were estimated with unconditional logistic regression.
Adjusted breast cancer odds were lower for the highest tertile of the SEI (OR = 0.47; 95% CI, 0.29-0.74). Results were similar within strata of estrogen receptor status. In analyses stratified by constitutive skin pigmentation, among participants with darker skin color, breast cancer risk was lower with more sun exposure (OR = 0.33; 95% CI, 0.16-0.70).
We found lower risk of breast cancer associated with greater sun exposure in a population living with high, continuous sun exposure. This beneficial finding should be placed in the context of other effects of sun exposure.
Sun exposure is a modifiable factor that may contribute, directly or indirectly, to lower breast cancer risk.
尽管证据不一致，但有证据表明，阳光暴露与降低乳腺癌风险有关。以前的研究是在紫外线辐射有季节性变化的地理区域进行的，包括低暴露甚至无暴露期，参与者主要是欧洲血统。波多黎各没有明显的季节性波动，持续暴露在非常高的紫外线辐射下。
我们在波多黎各圣胡安大都市区进行了一项基于人群的乳腺癌病例对照研究，研究了基于暴露和非暴露皮肤反射率比较的累积阳光暴露指数（SEI）。使用色度计测量皮肤反射率，并估计 307 例病例和 328 例对照中固有（未暴露）和兼性（暴露）皮肤色素之间的差异。通过访谈式问卷调查确定乳腺癌危险因素。使用非条件逻辑回归估计 OR 和 95%置信区间（CI）。
SEI 最高三分位的调整后乳腺癌比值较低（OR = 0.47；95%CI，0.29-0.74）。在雌激素受体状态的分层分析中，结果相似。在固有皮肤色素分层分析中，在肤色较深的参与者中，阳光暴露越多，乳腺癌风险越低（OR = 0.33；95%CI，0.16-0.70）。
我们发现，在一个长期暴露于高强度阳光的人群中，阳光暴露与乳腺癌风险降低相关。这一有益发现应放在阳光暴露其他影响的背景下考虑。
阳光暴露是一个可改变的因素，可能直接或间接导致乳腺癌风险降低。
