Reproductive and Hormonal Risk Factors for Breast Cancer in Blind Women
Final rept. 15 May 2004-14 Jul 2008
BRIGHAM AND WOMEN'S HOSPITAL BOSTON MA
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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, P0.01. These findings suggest that light may influence reproductive development in women and provides support for the hypothesis that light exposure at night is a risk factor for breast cancer.
- Anatomy and Physiology
- Medicine and Medical Research