WORK AND HEALTH:
SHIFT WORK AND CANCER:
Molly originally came upon this little gem in, of all places, the Winnipeg Sun. The Sun Media group took up this story and ran with it, adding their own simplifications, but also doing a great public service despite themselves by making people aware of epidemiological research on "carcinogenic work patters" even if in a distorted way. The original story came from the Associated Press, and slightly less sensationalist news outlets such as the Toronto Star reported the story under headlines such as 'WHO to list night shift as probable carcinogen'. Others went with far more dramatic headlines, and it seems that the story has been picked up by every news outlet worldwide. None of the mass media stories give the reader any directions to the original source of the story so that one could read and judge on one's own. Molly will here, but first it must be noted that the whole idea behind this story is hardly "news" if that term is to mean a truly new and startling development. Researchers have been at work for decades now ever since R. G. Stevens first proposed his hypothesis of an hormonal link between breast cancer and night work back in 1987 (R.G. Stevens, 'Electric power use and breast cancer', American Journal of Epidemiology 1987; 125 : 556-61). For a good summary of the evidence regarding breast cancer see 'Shift Work and Breast Cancer' (a 2003 report by the British Institute of Cancer Research in a downloadable pdf format). Most research has focused on such common cancers as breast cancer and prostrate cancer (see 'Shift Work Raises Prostrate Cancer Risk' at Medical News Today in 2006), though there have also been studies of the epidemiology of bowel cancer in relation to shift work.
The field is actually quite mature, and an epidemiological connection between shift work and a higher risk for at least the more common forms of cancer is pretty well established. the presumed mechanism is via disruption of circadian rhythms and a consequent disruption of the production of melatonin as well as the deregulation of circadian period genes involved as either cancer suppressors or promoters. Lack of melatonin also leads to a degree of immunosuppression which, if you believe the 'immune surveillance' theory of tumour suppression, would predispose the person or animal to malignant tumours. The latter is interesting, as animal(rodents) models show a "major" increase in tumour development by various experimental models using various ways of disrupting circadian rhythms.
The original consensus paper upon which the various recent mass media reports are based was produced by an October 2007 meeting of the International Agency for Research on Cancer, a branch of the World Health Organization (WHO) held in Lyon France. The full monographs are published in the December edition of The Lancet Oncology. Molly wants to make it known to her readers that the original summary is available free of charge online by subscribing to The Lancet online. By doing this (even without the "premium subscription") you can see the justification for the mass media reports with your own eyes. The summary notes that 15-20% of the population of Europe and the USA is engaged in shiftwork that involves nightwork, a horrifying statistic to Molly's beady little feline eyes. It should be noted that it isn't "nightwork" by itself that is so carcinogenic but rather nightwork that is truly "shift"-work in that the times of work (and therefore sleep) are regularly shifted such that the worker is periodically taken "off-balance" in a biological (and chronological) sense. Being the classic 'night-owl', Molly would see very little problem with getting her melatonin fix by sleeping from 8:00 am to 4:00 pm, but she would go nuttier than a fruitcake having to endure the "switches" in time such as people like nurses or railway workers do.
Molly highly recommends that her readers consult the original source given above if they have any interest in what the mass media has reported recently. In their report the study basically says that "shift-work" will be classified as a "probable" cancer risk. This may seems trifling to those unaccustomed to the terminology. There are actually very few "definite" risks for cancer. Most of the risks that people associate with that term are "probable" at best. The term "probable" carries a lot more weight in this context than it does in ordinary language. I also urge the reader to consult the report/monograph for the 2/3rds of it that were left out of the mass media reports. Working as either a painter or a firefighter are also recommended to be classified as "probable cancer risks". This may seem to be common sense, a hell of a lot more common and sensible than what people often go on about in their cancer fears. Yet the burden of proof is such that there are dozens (hundreds ???) of legal cases ongoing today about such workplace cancers and the rights of the workers to compensation. Looks like the lawyers for the plaintiffs will have the heavy cannons on their side in the near future.
Would such a thing as "night-work" exist in a society where workplaces were controlled democratically ? To my mind the answer is an obvious "yes". There are some services that very plainly have to be carried out 24/7, though gas bars and 7/11s are probably not amongst them. Would there be, however, any such workplaces where people were arbitrarily shifted from one work/play/sleep cycle to another ? Once more, to my mind the answer is obvious- NO. Seems very much like cruel and unusual punishment to me. The cruelty of such arrangements may not be as obvious and immediate as those of extended hours of work, but the results can be even more detrimental. Have a look at the Lancet article referenced above.