Night Shift Work and Risk of Breast Cancer
- 865 Downloads
Purpose of Review
Night work is increasingly common and a necessity in certain sectors of the modern 24-h society. The embedded exposure to light-at-night, which suppresses the nocturnal hormone melatonin with oncostatic properties and circadian disruption, i.e., misalignment between internal and external night and between cells and organs, are suggested as main mechanisms involved in carcinogenesis. In 2007, the International Agency for Research on Cancer (IARC) classified shift work that involves circadian disruption as probably carcinogenic to humans based on limited evidence from eight epidemiologic studies on breast cancer, in addition to sufficient evidence from animal experiments. The aim of this review is a critical update of the IARC evaluation, including subsequent and the most recent epidemiologic evidence on breast cancer risk after night work.
After 2007, in total nine new case-control studies, one case-cohort study, and eight cohort studies are published, which triples the number of studies. Further, two previous cohorts have been updated with extended follow-up. The assessment of night shift work is different in all of the 26 existing studies. There is some evidence that high number of consecutive night shifts has impact on the extent of circadian disruption, and thereby increased breast cancer risk, but this information is missing in almost all cohort studies. This in combination with short-term follow-up of aging cohorts may explain why some cohort studies may have null findings. The more recent case-control studies have contributed interesting results concerning breast cancer subtypes in relation to both menopausal status and different hormonal subtypes. The large differences in definitions of both exposure and outcome may contribute to the observed heterogeneity of results from studies of night work and breast cancer, which overall points in the direction of an increased breast cancer risk, in particular after over 20 years of night shifts.
Overall, there is a tendency of increased risk of breast cancer either after over 20 years of night shift or after shorter periods with many consecutive shifts. More epidemiologic research using standardized definitions of night work metrics and breast cancer subtypes as well as other cancers is needed in order to improve the epidemiologic evidence in combination with animal models of night work. Also, evidence-based preventive interventions are needed.
KeywordsCircadian disruption Light-at-night Breast cancer Shift work Melatonin
Compliance with Ethical Standards
Conflict of Interest
Johnni Hansen declares no conflict of interest.
Human and Animal Rights and Informed Consent
This article does not contain any studies with human or animal subjects performed by any of the authors.
Papers of particular importance, published recently, have been highlighted as: • Of importance •• Of major importance
- 4.Cancer IAfRo. Painting, firefighting, and shiftwork. IARC Monogr Eval Carcinog Risks Hum. 2010;98:9–764.Google Scholar
- 13.Chang AM, Scheer FA, Czeisler CA. The human circadian system adapts to prior photic history. J Physiol. 2011;Google Scholar
- 16.Bracci M, Manzella N, Copertaro A, Staffolani S, Strafella E, Barbaresi M, et al. Rotating-shift nurses after a day off: peripheral clock gene expression, urinary melatonin, and serum 17-beta-estradiol levels. Scand J Work Environ Health. 2014;40(3):295–304. doi: 10.5271/sjweh.3414.CrossRefPubMedGoogle Scholar
- 17.Devore EE, Warner ET, Eliassen H, Brown SB, Beck AH, Hankinson S, et al. Urinary melatonin in relation to postmenopausal breast cancer risk according to melatonin 1 receptor status. Cancer Epidemiol Biomark Prev. 2016; doi: 10.1158/1055-9965.EPI-16-0630.
- 20.Cancer IAfRo. Preample. Lyon2006 2006.Google Scholar
- 24.Blask DE, Dauchy RT, Sauer LA, Krause JA, Brainard GC. Light during darkness, melatonin suppression and cancer progression. !Lost Data. 2002;23(Suppl 2):52–6.Google Scholar
- 27.Straif K, Silverstein M. Comparison of U.S. Occupational Safety and Health Administration standards and German Berufsgenossenschaften Guidelines for Preventive Occupational Health Examinations. Am J Ind Med. 1997;31(4):373–80. doi: 10.1002/(SICI)1097-0274(199704)31:4<373::AID-AJIM1>3.0.CO;2-X. [pii] CrossRefPubMedGoogle Scholar
- 35.Jensen MA, Garde AH, Kristiansen J, Nabe-Nielsen K, Hansen AM. The effect of the number of consecutive night shifts on diurnal rhythms in cortisol, melatonin and heart rate variability (HRV): a systematic review of field studies. Int Arch Occup Environ Health. 2016;89(4):531–45. doi: 10.1007/s00420-015-1093-3.CrossRefPubMedGoogle Scholar
- 36.Jensen MA, Hansen AM, Kristiansen J, Nabe-Nielsen K, Garde AH. Changes in the diurnal rhythms of cortisol, melatonin, and testosterone after 2, 4, and 7 consecutive night shifts in male police officers. Chronobiol Int. 2016:1–13. doi: 10.1080/07420528.2016.1212869.
- 38.•• Stevens RG, Brainard GC, Blask DE, Lockley SW, Motta ME. Breast cancer and circadian disruption from electric lighting in the modern world. CA Cancer J Clin. 2014;64(3):207–18. doi: 10.3322/caac.21218. The most comprehensive overview of concequences of light-at-night, shift-work, melatonin, circadian disruption on breast cancer risk CrossRefPubMedGoogle Scholar
- 46.Zhu Y, Brown HN, Zhang Y, Data L, Zheng T. Period3 structural variation: a circadian biomarker associated with breast cancer in young women. Cancer Epidemiol Biomark Prev. 2005;14(1):268–70.Google Scholar
- 48.Harma M, Koskinen A, Ropponen A, Puttonen S, Karhula K, Vahtera J, et al. Validity of self-reported exposure to shift work. Occup Environ Med. 2016; doi: 10.1136/oemed-2016-103902.
- 53.Grundy A, Richardson H, Burstyn I, Lohrisch C, Sengupta SK, Lai AS, et al. Increased risk of breast cancer associated with long-term shift work in Canada. Occup Environ Med. 2013; doi: 10.1136/oemed-2013-101482.
- 58.Pronk A, Ji BT, Shu XO, Xue S, Yang G, Li HL, et al. Night-shift work and breast cancer risk in a cohort of Chinese women. Am J Epidemiol. 2010;Google Scholar
- 62.Travis RC, Balkwill A, Fensom GK, Appleby PN, Reeves GK, Wang XS, et al. Night shift work and breast cancer incidence: three prospective studies and meta-analysis of published studies. J Natl Cancer Inst. 2016;108(12) doi: 10.1093/jnci/djw169.
- 70.•• Wegrzyn LR, Tamimi RM, Rosner BA, Brown SB, Stevens RG, Eliassen AH, et al. Rotating night shift work and risk of breast cancer in the Nurses’ Health studies. Am J Epidemiol. 2017; doi: 10.1093/aje/kwx140. The best cohort-study, including long-term follow-up on rotating night shift-work and breast cancer
- 73.Schernhammer ES. RE: night shift work and breast cancer incidence: three prospective studies and meta-analysis of published studies. J Natl Cancer Inst. 2017;109(4) doi: 10.1093/jnci/djx002.
- 74.Stevens RG. RE: night shift work and breast cancer incidence: three prospective studies and meta-analysis of published studies. J Natl Cancer Inst. 2017;109(4) doi: 10.1093/jnci/djw342.
- 75.Hansen J. RE: night shift work and breast cancer incidence: three prospective studies and meta-analysis of published studies. J Natl Cancer Inst. 2017;109(4) doi: 10.1093/jnci/djw344.
- 79.Papantoniou K, Castano-Vinyals G, Espinosa A, Aragones N, Perez-Gomez B, Ardanaz E, et al. Breast cancer risk and night shift work in a case-control study in a Spanish population. Eur J Epidemiol. 2015; doi: 10.1007/s10654-015-0073-y.
- 82.Emilie Cordina-Duverger AP, Guenel P, Fritschi L, Glass D, Grundy A, Spinelli J, Aronson K, Rabstein S, Harth V, Pesch B, Brüning T, Castaño-Vinyals G, Kogevinas M. Night shift work and breast cancer risk: a combined analysis of population-based case-control studies with complete shift-work histories using a common definition of night work. Occup Environ Med. 2016;73(Supp1):1. doi: 10.1136/oemed-2016-103951.619.CrossRefGoogle Scholar
- 86.Cordina-Duverger E, Koudou Y, Truong T, Arveux P, Kerbrat P, Menegaux F, et al. Night work and breast cancer risk defined by human epidermal growth factor receptor-2 (HER2) and hormone receptor status: a population-based case-control study in France. Chronobiol Int. 2016:1–5. doi: 10.3109/07420528.2016.1167709.
- 88.Mao L, Yuan L, Slakey LM, Jones FE, Burow ME, Hill SM. Inhibition of breast cancer cell invasion by melatonin is mediated through regulation of the p38 mitogen-activated protein kinase signaling pathway. Breast Cancer Res. 2010;12(6):R107. doi: 10.1186/bcr2794.CrossRefPubMedPubMedCentralGoogle Scholar
- 93.Ijaz SI, Verbeek J, Seidler A, Lindbohm ML, Ojajarvi A, Orsini N, et al. Night-shift work and breast cancer—a systematic review and meta-analysis. Scand J Work Environ Health. 2013; doi: 10.5271/sjweh.3371.
- 96.• Van Dycke KC, Rodenburg W, van Oostrom CT, van Kerkhof LW, Pennings JL, Roenneberg T, et al. Chronically alternating light cycles increase breast cancer risk in mice. Curr Biol. 2015;25(14):1932–7. doi: 10.1016/j.cub.2015.06.012. This is the most thorough study in order to demonstrate breast cancer risk in experimental animals after simulated shift-work CrossRefPubMedGoogle Scholar
- 103.Neil SE, Pahwa M, Demers PA, Gotay CC. Health-related interventions among night shift workers: a critical review of the literature. Scand J Work Environ Health. 2014; doi: 10.5271/sjweh.3445.
- 104.Touitou Y, Reinberg A, Touitou D. Association between light at night, melatonin secretion, sleep deprivation, and the internal clock: health impacts and mechanisms of circadian disruption. Life Sci. 2017; doi: 10.1016/j.lfs.2017.02.008.