Louise E Johns1, Michael E Jones2, Minouk J Schoemaker2, Emily McFadden2,3, Alan Ashworth4,5,6,7, Anthony J Swerdlow2,4. 1. Division of Genetics and Epidemiology, The Institute of Cancer Research, London, SM2 5NG, UK. louise.johns@icr.ac.uk. 2. Division of Genetics and Epidemiology, The Institute of Cancer Research, London, SM2 5NG, UK. 3. Nuffield Department of Primary Care Health Sciences, University of Oxford, Oxford, OX2 6GG, UK. 4. Division of Breast Cancer Research, The Institute of Cancer Research, London, SW3 6JB, UK. 5. Breast Cancer Now Research Centre at The Institute of Cancer Research, London, SW3 6JB, UK. 6. Division of Molecular Pathology, The Institute of Cancer Research, London, SW7 3RP, UK. 7. UCSF Helen Diller Family Comprehensive Cancer Center, San Francisco, CA, 94158, USA.
We thank the author for their comments on our article.[1] The questions we asked about light in the bedroom at night[2] were very similar to those used by Stevens in a case–control study of breast cancer.[3] It seems curious that when these measures of exposure showed evidence of an association in that study, they were considered to give “evidence that indicators of exposure to light at night may be associated with the risk of developing breast cancer“,[3] but, apparently, when similar measures of exposure do not show an association they “yield no evidence one way or the other” and are as useful as assessing exposure “on the basis of the flip of a coin”.[1]As in almost all questionnaire epidemiology, the questions give subjective and imperfect measures of exposure, but this does not make them “no evidence”—they are another brick in an imperfect, hard-to-build, wall, in trying to assess the light at night hypothesis.
Authors: Louise E Johns; Michael E Jones; Minouk J Schoemaker; Emily McFadden; Alan Ashworth; Anthony J Swerdlow Journal: Br J Cancer Date: 2018-01-23 Impact factor: 7.640