Shift-work: Nursing's sometimes silent partner
Article Outline
In mid-December 2007 the International Agency for Risk on Cancer (IARC) published in Lancet Oncology (the results of their recent evaluation of shift-work as a cancer risk in which “shift-work involving circadian disruption” was categorised a Group 2A cancer risk (probably carcinogenic to humans) Straif et al., 2007). Also in this category are agents such as ultra-violet light and inorganic lead compounds, mixtures such as the emissions from high temperature frying and diesel engine exhaust and the occupational exposure of hairdressers or barbers. This categorisation, however, cannot but help move shift-work related issues from the organisational to a much more personal level for the many nurses consistently working “shift-work involving circadian disruption”. But what is the basis of this decision and what is a “reasonable” level of concern for nurses whose work involves “night duty”?
In general, shift-work is part of the life of all clinicians and frequently accepted by those who do it as something that must be tolerated, but about which very little can be done. There is of course some level of self-selection – those who can’t tolerate the effects of shift-work either leave nursing or work their way to areas that minimise the amount of shift-work they do. Interestingly, although there has been much shift-work research “using” nurses as subjects, very few of these studies have been initiated by nurses or attempt to address questions of direct interest to nurses. In the main, shift-work studies have found nurses a convenient group for gender comparison when exploring questions originating from other industries or when exploring gender-based interests in the effects of shift-work. Consequently, until relatively recently shift-work has been nursing's rather silent partner, However, recent initiatives in areas such as driver safety within the transport industry (and debates about who is legally and thus financially responsible) and the increasing emphasis on the management of the risk associated with clinical decision making in health are starting to raise organisational interest in shift-work.
In most formal definitions shift-work is considered to be work conducted outside of normal business hours – in short, work commencing before 8
am and finishing before 6pm. In recent years increasing flexibility in work hours and associated arrangements has made this once very simple definition increasingly complex in its application, but essentially the idea remains the same. If you start work early or finish late you are now commonly considered to be a shift-worker. Industries that maintain a 24-h schedule of work – including large parts of the health and service sectors, the hospitality industry, manufacturing and mining industries – are commonly understood to be shift-working industries, and it is these groups that the recent IARC announcement directly affects, as circadian disruption involves moving the time of sleep from the 11p.m.–7a.m. cycle that is accepted as the norm in most developed societies and generally involves sleeping during daytime hours. Thus, the determination that “shift-work involving circadian disruption” is a probable cancer risk is only of direct relevance to those who work shift-work that involves night work. Although the next obvious questions may well ask what type of night work, how much, what hours, on what schedule, in the absence of any specific dose-response data in relation to the amount of shift-work (dose) that may “cause” cancer (response) (Pukkala & Harma, 2007), it may be useful to delve into the debate surrounding this categorisation before becoming too concerned about one's personal shift schedule.
The IARC is a medically based organisation whose role it is to evaluate the various cancer risks that are frequently identified by the broad spectrum of research available in any particular area. The work of the IARC has without doubt been influential in decreasing exposure to many potential carcinogens, however the location of the IARC within a medical context and its reliance on particular forms of analysis can be critiqued (Stewart, 2008) as influencing the group's perspective in some areas. Not perhaps surprisingly there is another perspective on this debate, originating from those who research shift-work from perspectives that do not share the construction of shiftwork as a potential cause of disease.
Since first reported in 2001 (Hansen, 2006), an increased risk of breast cancer associated with occupational shiftwork exposure has been ridentified in several studies (Schernhammer et al., 2001; Schernhammer, Kroenke, Laden, & Hankinson, 2006; Megdal, Kroenke, Laden, Pukkala, & Schernhammer, 2005; Davis & Mirick, 2006). Schernhammer et al. (2001) report the findings of analyses of data obtained through the Nurses Health Study – a prospective cohort study that commenced in 1989 and collected data in 2001 on the basis of self-report questionnaires – as follows: “the risk of breast cancer was found to be modestly elevated in women who worked for 20 or more years on rotating night shifts compared with those who never worked rotating night shifts” (p. 110).
Not unreasonably further epidemiological work was then undertaken, some of which substantiated the link and others that challenged it (Schwartzbaum, Ahiborn, & Feychting, 2007) from statistical and study design perspectives but and also on the lack of a common or clearly defined understanding of what shift-work, night work and associated circadian disruption were held to be within these studies. Of equal concern is the support of an as yet experimental hypothesis (Stevens, 1987) that links levels of melatonin (a light sensitive hormone secreted at night) with protection from cancer. This supports the argument that work at night in well-lit environments suppresses melatonin secretion and thus increases the risk of cancer. This position has been clearly articulated in a recent editorial published in the Scandinavian Journal of Work Environment & Health (Pukkala & Harma, 2007), which concludes with a call for additional data on all aspects of this debate.
The multiple views and clearly limited availability of data must substantiate the concerns of those who are aware of the multiple forms of shift-work and the vast differences in the work undertaken by those working night shifts. For example, many night nurses tend to work in darkened clinical environments to promote the sleep of patients, a circumstance commonly compared, without examination to the work circumstances of those working on a well-lit manufacturing line.
While the real level of risk and the basis for the recent IARC decision are as yet difficult to determine in detail (full arguments are published in monographs usually not available until 18 months after the initial Policy Watch announcement in the Lancet), the reported efforts of several shift-work researchers to move this listing from “shift-work” to “shift work involving circadian disruption” are appreciated. While it is not necessarily time to become overly alarmed about the potentially carcinogenic effects of “shift-work involving circadian disruption”, it may well be time for nursing to become much more alert to the information provided through the research of shift-work in general and the potential impact of such findings on the organisation of nursing work. It is certainly past time for us to be changing approaches to shift-work on the basis of what may seem to be “a good idea” – 12-h shifts for example – but that is another shift-work story!
References
- . Circadian disruption, shift work and the risk of cancer: A summary of the evidence and studies in Seattle. Cancer Causes Control. 2006;17:539–545
- . Risk of breast cancer after night- and shift work: Current evidence and ongoing studies in Denmark. Cancer Causes Control. 2006;17:531–537
- . Night work and breast cancer risk: A systematic review and meta-analysis. European Journal of Cancer. 2005;41:2023–2032
- . Does shift work cause cancer?. Scandinavian Journal of Work Environment & Health. 2007;33(5):321–323
- . Night work and risk of breast cancer. Epidemiology. 2006;17(1):108–111
- Rotating night shifts and risk of breast cancer in woman participating in the nurses’ health study. Journal of the National Cancer Institute. 2001;93:1563–1568
- . Cohort study of cancer risk among male and female shift workers. Scandinavian Journal of Work Environment & Health. 2007;33(5):336–349
- . Electric power use and breast cancer. American Journal of Epidemiology. 1987;125:556–561
- . Banding carcinogenic risks in developed countries: A procedural basis for qualitative assessment. Mutation Research. 2008;658:124–151
- Carcinogenicity of shift-work, painting and fire-fighting. The Lancet – Oncology. 2007;8:1065–1066
PII: S1322-7696(08)00011-5
doi:10.1016/j.colegn.2008.03.001
© 2008 Published by Elsevier Inc.
