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Journal ArticleDOI

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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Citations
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Journal ArticleDOI
TL;DR: Control of electron flux, prevention of bottlenecks in the respiratory chain and electron leakage contribute to the avoidance of damage by free radicals and seem to be important in neuroprotection, inflammatory diseases and, presumably, aging.

709 citations


Cites background from "Light-at-night, circadian disruptio..."

  • ...The precise mechanisms of cancer prevention remain to be elucidated (Stevens, 2009)....

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Journal ArticleDOI
TL;DR: A framework that focuses on the cross‐factoring of the ways in which artificial lighting alters natural light regimes (spatially, temporally, and spectrally), and the ways that light influences biological systems, particularly the distinction between light as a resource and light as an information source is proposed.
Abstract: The ecological impacts of nighttime light pollution have been a longstanding source of concern, accentuated by realized and projected growth in electrical lighting. As human communities and lighting technologies develop, artificial light increasingly modifies natural light regimes by encroaching on dark refuges in space, in time, and across wavelengths. A wide variety of ecological implications of artificial light have been identified. However, the primary research to date is largely focused on the disruptive influence of nighttime light on higher vertebrates, and while comprehensive reviews have been compiled along taxonomic lines and within specific research domains, the subject is in need of synthesis within a common mechanistic framework. Here we propose such a framework that focuses on the cross-factoring of the ways in which artificial lighting alters natural light regimes (spatially, temporally, and spectrally), and the ways in which light influences biological systems, particularly the distinction between light as a resource and light as an information source. We review the evidence for each of the combinations of this cross-factoring. As artificial lighting alters natural patterns of light in space, time and across wavelengths, natural patterns of resource use and information flows may be disrupted, with downstream effects to the structure and function of ecosystems. This review highlights: (i) the potential influence of nighttime lighting at all levels of biological organisation (from cell to ecosystem); (ii) the significant impact that even low levels of nighttime light pollution can have; and (iii) the existence of major research gaps, particularly in terms of the impacts of light at population and ecosystem levels, identification of intensity thresholds, and the spatial extent of impacts in the vicinity of artificial lights.

706 citations


Cites background from "Light-at-night, circadian disruptio..."

  • ...Exposure to light at night has been shown to disrupt the circadian cycle of hormone production in humans, particularly melatonin, which has been linked to an increase in cancer risk in shift-workers (Stevens, 1987, 2009; Megdal et al., 2005; Reiter et al., 2011)....

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Journal ArticleDOI
TL;DR: Findings on shift work, in relation to risks of CVD, metabolic syndrome and diabetes are also suggestive but not conclusive for an adverse relationship, making it difficult to draw general conclusions.
Abstract: Background Shift work, including night work, has been hypothesized to increase the risk of chronic diseases, including cancer, cardiovascular disease (CVD), metabolic syndrome and diabetes. Recent reviews of evidence relating to these hypotheses have focussed on specific diseases or potential mechanisms, but no general summary of the current data on shift work and chronic disease has been published. Methods Systematic and critical reviews and recent original studies indexed in PubMed prior to 31 December 2009 were retrieved, aided by manual searches of reference lists. The main conclusions from reviews and principle results from recent studies are presented in text and tables. Results Published evidence is suggestive but not conclusive for an adverse association between night work and breast cancer but limited and inconsistent for cancers at other sites and all cancers combined. Findings on shift work, in relation to risks of CVD, metabolic syndrome and diabetes are also suggestive but not conclusive for an adverse relationship. Conclusions Heterogeneity of study exposures and outcomes and emphasis on positive but non-significant results make it difficult to draw general conclusions. Further data are needed for additional disease endpoints and study populations.

514 citations


Cites background from "Light-at-night, circadian disruptio..."

  • ...responsible for the rise in breast cancer incidence seen in the industrialized world [3]....

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Journal ArticleDOI
TL;DR: The amount of pollution is strongly dependent on the spectral characteristics of the lamps, with the more environmentally friendly lamps being low pressure sodium, followed by high pressure sodium and most polluting are the lamps with a strong blue emission, like Metal Halide and white LEDs.

473 citations


Cites background from "Light-at-night, circadian disruptio..."

  • ...As seen, circadian disruption is also induced by light exposure at night and light at night is becoming a public health issue (Pauley, 2004; Stevens, 2009)....

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Journal ArticleDOI
20 Feb 2014-Immunity
TL;DR: Understanding the daily rhythm of the immune system could have implications for vaccinations and how the authors manage infectious and inflammatory diseases.

424 citations


Cites background from "Light-at-night, circadian disruptio..."

  • ...It has also been concluded that ‘shift work that involves circadian disruption is probably carcinogenic to humans’ (Straif et al., 2007) and can lead to higher incidence of cardiovascular disease and obesity (Karlsson et al., 2001; Stevens, 2009)....

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References
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Journal ArticleDOI
TL;DR: The change in the joint distribution of the four risk factors accounted for less than 40% of the increase observed from 1959–60 to 1983–87, suggesting the effects of otherpowerful risk factors.
Abstract: The incidence rate of breast cancer in Japan rose more than two-fold from 1959-60 to 1983-87. To assess to what extent this increase can be explained by changes in the prevalence of four major risk factors of breast cancer (i.e. age at menarche, age at first birth, age at menopause, and parity), we estimated the probability of developing breast cancer based on the joint distribution and relative risks of these four risk factors. The age-specific incidence rate during 1959-60 reported by the Miyagi Prefectural Cancer Registry was used to estimate the baseline hazard rate for women without the four risk factors in the same age group. Assuming that the baseline hazard rate is constant during all periods, we calculated the expected incidence rates during the periods of 1959-60, 1962-64, 1968-71, 1973-77, 1978-81, and 1983-87 for each age group. Large discrepancies were noted between the observed and expected incidence rates during 1983-87 in all age groups. The change in the joint distribution of the four risk factors accounted for less than 40% of the increase observed from 1959-60 to 1983-87, suggesting the effects of other powerful risk factors.

75 citations

Journal ArticleDOI
TL;DR: The results suggest that sensitivity of melatonin to light suppression is influenced by eye pigmentation and/or ethnicity.
Abstract: This experiment tested effects of human eye pigmentation depending on the ethnicity on suppression of nocturnal melatonin secretion by light. Ten healthy Caucasian males with blue, green, or light ...

71 citations

Journal ArticleDOI
TL;DR: Findings suggest that some aspects of night shift work may influence the development of endometriosis.
Abstract: BACKGROUND: Endometriosis, a dysplastic disease affecting approximately 5%-10% of US reproductive-age women, has been linked to exposures indicating high circulating estrogen levels. One such exposure may be night shift work, which has been associated with menstrual disruption and increased risk of 2 other estrogen-influenced diseases, breast cancer and adverse coronary events. METHODS: In this population-based case-control study, cases were 235 women aged 18 to 49 years who were enrolled in a large health-maintenance organization in the state of Washington, and who were first diagnosed with surgically-confirmed endometriotic disease between April 1, 1996 and March 31, 2001. Controls were 545 randomly selected women enrolled in the same program who did not have a history of endometriosis. Study participants were asked about night shift work in all paid full-time or part-time jobs they had worked from age 18 to the reference date. Genotypes for T3111C hCLOCK were determined for a subset of 218 cases and 456 controls. RESULTS: Any night shift work was associated with a 50% increase in risk of endometriosis (odds ratio = 1.48 [95% confidence interval = 0.96-2.29]), and working more than half of shifts on a job at night was associated with a nearly doubled disease risk (1.98 [1.01-3.85]). Changing sleep patterns on days off was associated with further increases in disease risk. T3111C hCLOCK polymorphism was unrelated to endometriosis status and did not modify the effect of shift work on endometriosis. CONCLUSIONS: These findings suggest that some aspects of night shift work may influence the development of endometriosis.

68 citations

Journal ArticleDOI
TL;DR: The meta-analysis confirmed the significantly increased risks for malignant melanoma and breast cancer in female FA and increased exposure to cosmic radiation during flight has been suggested as a potential occupational risk factor.
Abstract: Background Airline flight personnel work in a unique environment with exposure to known or suspected carcinogens and mutagens including ionizing cosmic radiation. A meta-analysis was conducted to study whether the occupational exposure of female flight attendants (FA) increased their relative risk of cancer incidence. Methods A bibliographical computer search from 1966 to 2005 of cancer incidence cohort studies of female FA was performed. Combined relative risks (RRc) in cancer incidence were calculated by means of meta-analysis. Results RRc and 95% confidence interval (CI) for malignant melanoma and breast cancer in female FA were 2.13 (95% CI: 1.58–2.88) and 1.41 (1.22–1.62) (p < 0.0001). Excess risk was not significant for all-site cancer with RRc of 1.10 (0.99–1.21). Conclusions The meta-analysis confirmed the significantly increased risks for malignant melanoma and breast cancer in female FA. Increased exposure to cosmic radiation during flight has been suggested as a potential occupational risk factor. Ultraviolet radiation exposure on board seems an unlikely occupational risk, but nonoccupational leisure time sun exposure is a possible risk factor. The etiology of the observed increase in incidence of some cancers remains controversial because assessment of possible confounders, especially nonoccupational exposure factors, has thus far been limited.

63 citations