Sleep duration, melatonin and breast cancer among Chinese women in Singapore

Abstract

Background: Sleep duration has been hypothesized to be inversely associated with breast cancer risk, possibly due to greater overall melatonin production in longer sleepers. However, data are inconclusive from the three studies conducted in Western populations on sleep duration and breast cancer risk. Methods: We investigated the relationship between self-reported usual sleep duration determined at baseline and subsequent risk of breast cancer in the prospective, population-based cohort of the Singapore Chinese Health Study. We excluded from the study women with