The observation that women who work at night have an increased breast cancer risk is intriguing, but the biological mechanisms explaining this association are not yet established.  One theory is that the hormone melatonin, which is produced at higher levels during periods of darkness, is inversely associated with breast cancer risk.  There is considerable experimental evidence to support the anti-cancer activities of melatonin.  However, results from the three recent observational cohort studies that have examined the relation between urinary levels of melatonin and breast cancer risk have been inconsistent, and additional evidence is needed to evaluate this promising, but as yet unconfirmed, association. We propose to conduct a nested case-control study of 284 invasive breast cancer cases and 568 control subjects within the WHI Observational Study (OS) to investigate if higher urinary levels of the melatonin metabolite 6-sulfatoxymelatonin are associated with a decreased risk of postmenopausal breast cancer.  This study is important to conduct in WHI because it is one of very few prospective cohorts that have urinary specimens collected to evaluate this hypothesis.  This nested case-control study will afford the opportunity to explore the association between levels of urinary melatonin and breast cancer risk by the time interval between urinary specimen collection and breast cancer development.  This study is important because it may lead to important new strategies to prevent breast cancer.

 

 

1. To examine the association between urinary levels of the melatonin metabolite 6-sulfatoxymelatonin (aMT6s) and risk of breast cancer