Light-at-night, circadian disruption and breast cancer: assessment of existing evidence
01 Aug 2009-International Journal of Epidemiology (Oxford University Press)-Vol. 38, Iss: 4, pp 963-970
TL;DR: 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.
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TL;DR: A recent review highlights the role of the circadian clock in tumorigenesis, cancer hallmarks and introduces the state-of-the-art in sleep-monitoring technologies, discussing the eventual application of insights in clinical settings and cancer research as mentioned in this paper .
Abstract: Circadian rhythms impose daily rhythms a remarkable variety of metabolic and physiological functions, such as cell proliferation, inflammation, and DNA damage response. Accumulating epidemiological and genetic evidence indicates that circadian rhythms' disruption may be linked to cancer. The integration of circadian biology into cancer research may offer new options for increasing cancer treatment effectiveness and would encompass the prevention, diagnosis, and treatment of this disease.In recent years, there has been a significant development and use of multi-modal sensors to monitor physical activity, sleep, and circadian rhythms, allowing, for the very first time, scaling accurate sleep monitoring to epidemiological research linking sleep patterns to disease, and wellness applications providing new potential applications. This review highlights the role of circadian clock in tumorigenesis, cancer hallmarks and introduces the state-of-the-art in sleep-monitoring technologies, discussing the eventual application of insights in clinical settings and cancer research.
7 citations
31 Dec 2016
TL;DR: Kim et al. as discussed by the authors presented a joint research with Professor Jeong Tai Kim, Kyung Hee University, Republic of Korea, Korea. They used a novel approach to study the relationship between the two domains.
Abstract: Joint research with Professor Jeong Tai Kim, Kyung Hee University, Republic of Korea.
This is an Open Access journal
7 citations
Cites background from "Light-at-night, circadian disruptio..."
...breast and colo-rectal), because light at night can alter the brain’s biochemistry by the inhibiting production of Melatonin, (an antioxidant that protects the body from certain cancers) [2-5]3....
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TL;DR: The results suggest that the susceptibility to tumor initiation and/or growth may be related to individual differences in baseline immune and endocrine physiology and emotional tone present at the time of carcinogen exposure.
6 citations
Cites background from "Light-at-night, circadian disruptio..."
...Understanding the role of individual differences in physiological or behavioral traits on cancer susceptibility is particularly relevant for cancers for which no singular cause has been identified (e.g., breast cancer; Stevens, 2009)....
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TL;DR: In this paper, it was shown that exposure to light at night suppresses pineal melatonin secretion, potentially reversing the normally oncostatic properties of the hormone and increasing circulating oestrogens associated with breast carcinogenesis, and further applied to aspects of desynchronisation of the master circadian pacemaker with peripheral oscillators due to slow adaption and synchronisation to rapid transitions between different shift schedules, different expressions in circadian genes, and sleep deprivation followed by night shift work in initiating or promoting breast cancer and probably other cancers.
Abstract: Electrical light, which has been a widespread benefit only during about the past 100 years, is new in an evolutionary perspective, and has among priceless advantages given humans the ability to work during the normal dark part of the day (evening, night and early morning). In the late 1980s Stevens1 suggested that exposure to light at night may increase the risk of breast cancer. The initial hypothesis was that exposure to light at night suppresses pineal melatonin secretion, potentially reversing the normally oncostatic properties of the hormone and increasing circulating oestrogens associated with breast carcinogenesis. Later, this hypothesis was further applied to aspects of desynchronisation of the master circadian pacemaker (suprachiasmatic nucleus) with peripheral oscillators due to slow adaption and synchronisation to rapid transitions between different shift schedules, different expressions in circadian genes, and sleep deprivation followed by night shift work in initiating or promoting breast cancer and probably other cancers.2 The first epidemiological studies testing Steven's hypothesis were published in 2001, and all three independent studies from Denmark and the USA showed significantly increased breast cancer risks, including a dose-related increase in risk with increasing years of non-daytime work.3 In October 2007, an expert group from 10 countries convened by the International Agency …
6 citations
TL;DR: In this article, the spatial and temporal patterns of outdoor LAN exposure changes across the Republic of Korea (ROK), a developing country in Asia, between 1995 and 2010, and incorporated the population and its demographic characteristics of light exposure in this research.
Abstract: Outdoor light at night (LAN) would be a public concern potentially associated with adverse health outcomes mainly in developed countries, but it might also be an environmental health issue in developing countries. However, there have been few studies reporting the spatial and temporal aspects of LAN level changes incorporated with population exposure in such nations. Therefore, we analyzed the spatiotemporal patterns of outdoor LAN exposure changes across the Republic of Korea (ROK), a developing country in Asia, between 1995 and 2010. In addition, we incorporated the population and its demographic characteristics of light exposure in this research. We utilized Defense Meteorological Satellite Program (DMSP) Operational Linescan System (OLS) observations as a spatial proxy of LAN and the ROK census data. This research observed 57.6% (≈57,800 km2) of land areas in the country to experience increases in outdoor artificial illumination at nights. The highest levels of LAN were found to affect about 58% of th...
6 citations
Cites background from "Light-at-night, circadian disruptio..."
...…1, 69–78, http://dx.doi.org/10.1080/15230406.2014.987695 © 2014 Cartography and Geographic Information Society cancers particularly in developed countries (Kerenyi, Pandula, and Feuer 1990; Stevens and Rea 2001; Schernhammer and Schulmeister 2004; Stevens 2005; Reiter et al. 2009; Stevens 2009a)....
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...Taking those findings into account, now we need to investigate the potential associations between light pollution and negative health outcomes among the ROK population, particularly for LAN-associated BC research (Stevens 2009b)....
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TL;DR: Findings establish that the human response to light is qualitatively similar to that of other mammals.
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TL;DR: The results suggest that, in humans, a single photopigment may be primarily responsible for melatonin suppression, and its peak absorbance appears to be distinct from that of rod and cone cellphotopigments for vision.
Abstract: The photopigment in the human eye that transduces light for circadian and neuroendocrine regulation, is unknown. The aim of this study was to establish an action spectrum for light-induced melatonin suppression that could help elucidate the ocular photoreceptor system for regulating the human pineal gland. Subjects (37 females, 35 males, mean age of 24.5 +/- 0.3 years) were healthy and had normal color vision. Full-field, monochromatic light exposures took place between 2:00 and 3:30 A.M. while subjects' pupils were dilated. Blood samples collected before and after light exposures were quantified for melatonin. Each subject was tested with at least seven different irradiances of one wavelength with a minimum of 1 week between each nighttime exposure. Nighttime melatonin suppression tests (n = 627) were completed with wavelengths from 420 to 600 nm. The data were fit to eight univariant, sigmoidal fluence-response curves (R(2) = 0.81-0.95). The action spectrum constructed from these data fit an opsin template (R(2) = 0.91), which identifies 446-477 nm as the most potent wavelength region providing circadian input for regulating melatonin secretion. The results suggest that, in humans, a single photopigment may be primarily responsible for melatonin suppression, and its peak absorbance appears to be distinct from that of rod and cone cell photopigments for vision. The data also suggest that this new photopigment is retinaldehyde based. These findings suggest that there is a novel opsin photopigment in the human eye that mediates circadian photoreception.
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