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Abstract:
We read with great interest the recently published article “Domestic light at night and breast cancer risk: a prospective analysis of 105000 UK women in the Generations Study” by Johns et al.1 The study examined the relationship between breast cancer risk and self-reported levels of artificial light in the bedroom, and the 95% confidence levels of the hazard ratios that were consistent with little or no effect. In this letter, we would like to draw attention to a major problem with the instrument used for the subjective estimation of light exposure, and to suggest a different instrument for future studies.
