Risk of breast cancer among Norwegian women with visual impairment

Experimental studies suggest that melatonin has a protective effect against breast cancer. Exposure to light suppresses melatonin secretion, but to a lesser degree in totally blind persons. Breast cancer was investigated in a cohort of 15 412 Norwegian visually impaired women. The risk among totally blind women was 0.64 (95% CI = 0.21–1.49, 5 cases only), and for those who became blind before age of 65, the SIR was 0.51 (95% CI = 0.11–1.49). Our findings give support to the ‘melatonin hypothesis’. © 2001 Cancer Research Campaign http://www.bjcancer.co

Sleep duration and the risk of breast cancer: the Ohsaki Cohort Study

In a prospective study of 23 995 Japanese women, short sleep duration was associated with higher risk of breast cancer (143 cases), compared with women who slept 7 h per day, the multivariate hazard ratio of those who slept ⩽6 h per day was 1.62 (95% confidence interval: 1.05–2.50; P for trend=0.03)