Reproductive and Hormonal Risk Factors for Breast Cancer in Blind Women

摘要

Epidemiological observations indicate that breast cancer risk is lower in visually impaired women compared to sighted women and that risk is inversely correlated with degree of visual impairment. A hypothesis to explain these findings is that blind people are less susceptible to suppression of melatonin by light exposure at night and therefore have higher levels of melatonin. Melatonin has oncostatic properties in vitro. In a survey of blind women, we found that blind women with no perception of light (NPL) have a reduced risk of breast cancer compared to blind women with light perception (LP) (OR = 0.45 CI: 0.25, 0.80). In adjusted analyses the effect was consistent, but attenuated (OR = 0.56, CI: 0.30, 1.02). When we stratified the data at age 50, we found a significantly lower risk among women over age 50 in adjusted analyses (OR = .40, CI: .22, .74). These differences could not be explained by differences in known reproductive risk factors for breast cancer. In contrast, NPL women appear to have risk factors consistent with an elevated risk, including an earlier reported menarche than LP women (NPL = 12.18 1.53 years vs. 12.46 1.57 years, P).