Army Nurse Operating Medical Equipment at Camp Bastion Hospital, Afghanistan--via Flickr (Defence Images)
Army Nurse Operating Medical Equipment at Camp Bastion Hospital, Afghanistan–via Flickr (Defence Images)

Working night shifts may be bad for your body’s internal clock and your social life, but one thing it apparently doesn’t do, at least according to new research from Cancer Research UK, is cause breast cancer. Cancer Research combined the results of 10 different studies around the world (three of which were brand new) and included key information about working hours among a group of British women who were then followed up via NHS records. Combining all 10 of these studies, the CRUK scientists were able to draw conclusions from data that included more than 1.4 million women and found they could not substantiate any link between working nights and breast cancer.

The Cancer Research findings come after years of debate over whether working at night endangers women’s’ health, and it specifically contravenes advice given by the International Agency for Research on Cancer (IARC), the specialized cancer arm of the World Health Organization (WHO). In 2007, IARC stated that shift work involving circadian disruption is “probably carcinogenic to humans” and detailed how epidemiological studies found that long-term female night-workers (including nurses and flight attendants) “have a higher risk of breast cancer risk than women who do not work at night.” Their studies suggested a relationship between the sleep hormone melatonin and the genes that control tumor development. It also suggested that exposure to artificial light may affect the production of estrogen, which can also induce hormone sensitive tumors in the breast. There was also bad news for painters and firefighters, who were also listed as being at risk of developing cancer because of the substances they are exposed to.

The newer research from Cancer Research UK represents a shift in the available evidence, and it raises the question of whether IARC will change its mind. The night work debate is just one of many controversies the WHO body has recently gotten mixed up in. Late last year, it set off a bacon-flavored firestorm by announcing that every 50-gram portion of processed meat eaten daily increased risk of colorectal cancer by 18%. IARC also recently backtracked on assertions that coffee was a carcinogen. The stream of headlines and disputed findings has thrust IARC so far into the spotlight that the National Institutes of Health (NIH), the US government’s health research agency, is now being questioned by a Congressional oversight committee over why American taxpayers are funding an agency that faces so much criticism. Writing to the NIH, committee chair Jason Chaffetz pointed out that IARC’s standards and classifications of carcinogens “appear inconsistent with other scientific research, and have generated much controversy and alarm.”

If IARC’s findings provoke so much media attention and handwringing, it is in part because those pronouncements have real policy implications and economic consequences. Denmark, for example, started offering female night workers who have developed breast cancer compensation on the basis of the IARC findings. Flight attendant Ulla Mahnkopf, who spent three decades working for the Scandinavian airline SAS, was one of the women who were awarded damages after a breast cancer diagnosis.

In the US, the National Institute for Occupational Safety and Health (NIOSH) decided in 2012 that the 70,000 surviving firefighters, police officers and other first responders to the World Trade Center after the September 11 attacks would be entitled to free monitoring and treatment for some 50 forms of cancer, drawing directly off IARC findings. Employer rights groups are also quick to act based on any new developments regarding work patterns and employee health. Responding to the IARC breast cancer findings in 2012, Brendan Barber of the UK’s Trade Union Congress (TUC) said that his organization needed “urgent advice from the [Health and Safety Executive] and government so that employers can reduce the risk of female workers developing breast cancer, for example by identifying safer shift patterns.”

Of course, there is another drawback to disputed results: in focusing on cancer hazard (the possibility that something could cause cancer, not that it will) or lack thereof, we risk ignoring the other very real issues working at night presents. The issue of compensating hardworking nurses, flight attendants, and others for breast cancer diagnoses speaks to just how high the stakes can be. Those women’s cancer issues might not directly link to their work schedules, but there are plenty of other health issues they (and their colleagues) have had to face that we should all be cognizant of.

Night shifts, even if they do not cause cancer, have been linked to conditions like heart disease, diabetes, and a heightened risk of obesity. These dangers are both environmental and physical. A study published in the Proceedings of the National Academy of Sciences (PNAS) indicated that sleep patterns even affect molecular mechanisms and gene expression, while another study showed night workers have a “heightened preference” for high fat foods. Stress and depression are also common side effects of trying to sleep when the world is awake. Developing psychiatric conditions due to accumulated sleep debt is not uncommon, especially as “things get to a point where [sleep debt] begins to…impact on social function and relationships.”

If it has managed to beat the cancer rap, working at night can nonetheless contribute to a premature death. In a study on the impact of shift patterns published in the American Journal of Preventative Medicine, a study of 74,862 nurses found that, after 22 years, the nurses who worked on rotating night shifts for more than five years were up to 11% more likely to die early compared to those who never worked these shifts.

This is all important knowledge and solidly in the public interest, but it all too often drowned out by the miasma of misunderstood – and sometimes willfully misreported – health research which suggests pretty much all aspects of modern life is bad for you. In the face of such negativity, taking responsibility for the actual health risks we expose ourselves to might seem like a herculean task. What we need is better reported, more precise information about what ails us and what we can do about it. Otherwise, misperceptions will continue to impact business, policymaking, and individual quality of life.