scispace - formally typeset
Search or ask a question
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.

Content maybe subject to copyright    Report

Citations
More filters
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)....

    [...]

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)....

    [...]

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]....

    [...]

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)....

    [...]

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)....

    [...]

References
More filters
Journal ArticleDOI
TL;DR: The hypothesis that use of electric power may increase risk of breast cancer is presented based on experimental evidence that shows an effect of light and extremely low frequency electric and/or magnetic fields on pineal melatonin production, and on the relationship of melatonin to mammary carcinogenesis.
Abstract: It is the purpose of this paper to present the hypothesis that use of electric power may increase risk of breast cancer. The hypothesis is based on experimental evidence that shows an effect of light and extremely low frequency electric and/or magnetic (ELF) fields on pineal melatonin production, and on the relationship of melatonin to mammary carcinogenesis. A brief discussion of the epidemiology of breast cancer will be followed by a description of the experimental foundation for the hypothesis. 20 references, 1 figure.

487 citations

Journal ArticleDOI
TL;DR: The odds ratio for breast cancer among women who worked at night at least half of a year was 1.5 (95% confidence interval, 1.2 to 1.7), and there was a tendency to increasing odds ratio by increasing duration of nighttime employment.
Abstract: Irregular working hours, including working at night, have serious psychological and physiological effects. In a nationwide population-based case-control study, we investigated the breast cancer risk among 30- to 54-year-old Danish women who worked predominantly at night. Individual employment histories were reconstructed back to 1964 for each of 7035 women with breast cancer and their individually matched controls from the records of a nationwide pension scheme with compulsory membership. Odds ratios, including 5 years of induction time and adjusted for socio-economic status, age at the birth of first and last child and number of children, were estimated by conditional logistic regression analysis. The odds ratio for breast cancer among women who worked at night at least half of a year was 1.5 (95% confidence interval, 1.2 to 1.7), and there was a tendency to increasing odds ratio by increasing duration of nighttime employment.

481 citations

Journal ArticleDOI
TL;DR: The existing empirical data seem to be compatible with the hypothesis that increased concentrations of oestrogens in pregnancy increase the probability of future occurrence of breast cancer in daughters.

464 citations

Journal ArticleDOI
TL;DR: Women who reported more than 20 years of rotating night shift work experienced an elevated relative risk of breast cancer compared with women who did not report any rotating nightShift work.
Abstract: Background: Melatonin shows potential oncostatic activity and is acutely suppressed by light exposure. Some evidence suggests an association between night work and breast cancer risk, possibly through the melatonin pathway. Methods: In a cohort of premenopausal nurses, we prospectively studied the relation between rotating night shift work and breast cancer risk. Total number of months during which the nurses worked rotating night shifts was first assessed at baseline in 1989 and periodically updated thereafter. We used Cox proportional hazards models to calculate relative risks (RRs) and 95% confidence intervals (CIs). Results: Among 115,022 women without cancer at baseline, 1,352 developed invasive breast cancer during 12 years of follow up. Women who reported more than 20 years of rotating night shift work experienced an elevated relative risk of breast cancer compared with women who did not report any rotating night shift work (multivariate RR 1.79; 95% CI 1.06‐3.01). There was no increase in risk associated with fewer years of rotating night work. Conclusion: Our results suggest a modestly elevated risk of breast cancer after longer periods of rotating night work. Additional studies are warranted to rule out small sample size or uncontrolled sources for confounding as alternative explanations.

463 citations

Journal ArticleDOI
TL;DR: There is evidence of an interaction (deviation from the logistic regression‐postulated multiplicativity) between obesity and age at menarche, implying that the protective effect of late menarches may not apply to overweight women or that late menrche may become detrimental in obese women.
Abstract: The importance of age at menarche, age at menopause, height, and obesity as risk factors for breast cancer, and the possible interactions among these factors in breast cancer causation were investigated in a data set collected in the late 1960's, in an international multicenter case-control study. Multiple logistic regression procedures were used to model data from 3,993 breast cancer cases and 11,783 controls from 7 study centers representing the range of international variation of breast cancer incidence. Height and obesity (measured through the weight/height2 index) were independent risk factors for breast cancer among post-menopausal but not pre-menopausal women; post-menopausal women taller by 10 cm had a 12% higher risk of breast cancer (95% confidence interval, CI, 3-21%) and post-menopausal women of average height (say 158 cm) had an 11% higher risk of breast cancer (CI 7-16%) when they were heavier by 10 kg (and, therefore, more obese by 4 kg/m2). Age at menarche was a risk factor among both pre-menopausal and post-menopausal women, a delay of 2 years corresponding to a 10% reduction in breast cancer risk (CI 6-15%). Age at menopause was also a breast cancer risk factor, women with menopause at each 5 year age difference having a 17% higher risk of breast cancer (CI 11-22%). There is evidence of an interaction (deviation from the logistic regression-postulated multiplicativity) between obesity and age at menarche, implying that the protective effect of late menarche may not apply to overweight women or that late menarche may become detrimental in obese women. The estimated relative risk coefficients, when applied to average risk factor levels observed among control women, can explain only a small fraction of the difference in breast cancer incidence between Boston and Tokyo.

399 citations