Light-at-night, circadian disruption and breast cancer: assessment of existing evidence
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TLDR
If a consensus eventually emerges that LAN does increase risk, then the mechanisms for the effect are important to elucidate for intervention and mitigation and will provide for the development of lighting technologies at home and at work that minimize circadian disruption, while maintaining visual efficiency and aesthetics.Abstract:
Background Breast cancer incidence is increasing globally for largely unknown reasons. The possibility that a portion of the breast cancer burden might be explained by the introduction and increasing use of electricity to light the night was suggested >20 years ago.
Methods The theory is based on nocturnal light-induced disruption of circadian rhythms, notably reduction of melatonin synthesis. It has formed the basis for a series of predictions including that non-day shift work would increase risk, blind women would be at lower risk, long sleep duration would lower risk and community nighttime light level would co-distribute with breast cancer incidence on the population level.
Results Accumulation of epidemiological evidence has accelerated in recent years, reflected in an International Agency for Research on Cancer (IARC) classification of shift work as a probable human carcinogen (2A). There is also a strong rodent model in support of the light-at-night (LAN) idea.
Conclusion If a consensus eventually emerges that LAN does increase risk, then the mechanisms for the effect are important to elucidate for intervention and mitigation. The basic understanding of phototransduction for the circadian system, and of the molecular genetics of circadian rhythm generation are both advancing rapidly, and will provide for the development of lighting technologies at home and at work that minimize circadian disruption, while maintaining visual efficiency and aesthetics. In the interim, there are strategies now available to reduce the potential for circadian disruption, which include extending the daily dark period, appreciate nocturnal awakening in the dark, using dim red light for nighttime necessities, and unless recommended by a physician, not taking melatonin tablets.read more
Citations
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Dim light at night disrupts molecular circadian rhythms and increases body weight.
Laura K. Fonken,Taryn G. Aubrecht,O. Hecmarie Meléndez-Fernández,Zachary M. Weil,Randy J. Nelson +4 more
TL;DR: Evidence is provided that mild changes in environmental lighting can alter circadian and metabolic function and detailed analysis of temporal changes induced by nighttime light exposure may provide insight into the onset and progression of obesity and metabolic syndrome, as well as other disorders involving sleep and circadian rhythm disruption.
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Night Work and the Risk of Cancer Among Men
TL;DR: It is suggested that night work may increase cancer risk at several sites among men, with risks generally being increased across all duration categories.
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Timing of light exposure affects mood and brain circuits
TL;DR: This review focuses on the role of artificial light at night in mood regulation, including mechanisms through which aberrant light exposure affects the brain, and summarizes the evidence linking aberrantLight exposure to mood.
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Sirtuins, melatonin and circadian rhythms: building a bridge between aging and cancer
TL;DR: Evidence is provided for a possible connection between sirtuins, melatonin, and the circadian rhythm circuitry and their implications in aging, chronomodulation, and cancer.
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Case–control study of shift-work and breast cancer risk in Danish nurses: Impact of shift systems
Johnni Hansen,Richard G. Stevens +1 more
TL;DR: The results provide further evidence that night shift-work may increase the risk for breast cancer and suggest that the largest impact on risk is associated with the most disruptive shifts.
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