A high estimated night-time exposure to outdoor artificial light in the blue-enriched light spectrum increases the risk of breast and prostate cancer

In April 2018 researchers from Spain, Canada and UK assessed the association between artificial light at night during sleeping time with risk of breast and prostate cancer in Spanish individuals. A total of 1,219 individuals with breast cancer, 1,385 female controls, 623 prostate cancer cases, and 879 male controls who had never worked at night were involved in the study. Information on artificial light at night was analysed using images from the International Space Station, available for Barcelona and Madrid for 2012 and 2013, plus data on remotely sensed upward light intensity and blue light spectrum for the postcode of each individual. Results showed that individuals living in Barcelona and Madrid had been exposed to night time outdoor artificial light in the blue light spectrum. It was also seen that these individuals had an increased risk of both breast and prostate cancer. In contrast, when exposure to the highest versus lowest intensity of outdoor light was compared, those individuals with the highest exposure were more likely to be in the control group than those diagnosed with cancer, particularly prostate cancer. A further analysis revealed that, compared with those who reported sleeping in total darkness, men who slept in “quite illuminated” bedrooms had a higher risk of prostate cancer whereas women had a slightly lower risk of breast cancer.

Garcia-Saenz A et al. Evaluating the Association between Artificial Light-at-Night Exposure and Breast and Prostate Cancer Risk in Spain (MCC-Spain Study). Environ Health Perspect. 2018 Apr 23;126(4):047011

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