Working the night shift could potentially double your risk of breast cancer, reports based on a new study are claiming. So what are the facts behind this scare story?
The study, published in the journal Occupational and Environmental Medicine, is based on an analysis of Canadian women and found an increased risk in breast cancer in women who had worked the night shift for 30 years or more.
Obviously, that excludes the majority of women. Nevertheless, the particulars of the study are interesting.
Previous research has already found that nurses who, over a sustained number of years, consistently worked the night shift are at a higher risk of breast cancer.
The researchers in this study — with teams from the Queen’s Cancer Research Institute, Queen’s University, Ontario, and the School of Public Health, Drexel University, Philadelphia, among several others — examined the work histories of 1134 breast cancer patients and 1179 controls, or women who had never had breast cancer.
This time they did not limit themselves to nurses.
They found that those women who worked the night shift for up to 30 years did not have a significant increase in breast cancer rates. However, for those who worked the night shift over thirty years, the risk of breast cancer in some cases as much as doubled.
The cause of this, the researchers say, might actually be quite simple: light.
They hypothesize that a lack of melatonin, a hormone thought to have cancer protecting qualities, may be playing a part.
Significantly, melatonin production is reduced when we are exposed to light. Nurses and those in other night shift-dependent professions would therefore likely be exposed to more light as they go from a daytime environment to their nighttime work under artificial light.
However, the researchers are keen to point out that this study is not definitive and that more research will be needed before they can establish what is known as a direct causal link.
This is something that Dr Hannah Bridges, from leading charity Breakthrough Breast Cancer, echoed, saying:
“This is one of a few studies that suggest working night shifts for many years may increase breast cancer risk. However, we don’t yet know that shift work is a risk factor for breast cancer, so we’d urge women not to panic. We need to better understand why night work might increase breast cancer risk.”
Indeed, the researchers note that the increase in breast cancer rates may not be down to a lack of melatonin alone.
Sleep cycle interruption has been demonstrated to create a variety of health problems. Based on previous evidence, we also know that those who work the night shift are more likely, though of course not certain, to have poorer diets and are less likely to exercise regularly.
Further, and as in the case of nursing, jobs that require the night shift can often be high pressure. That, in turn, creates all the associated and possibly health damaging reactions the body is known to suffer, such as cortisol release, a known suspect in cancer deaths.
As such, and as is the common advice when faced with most health complaints, the increased risk association in this study linking the night shift with breast cancer might be mitigated by regular exercise and a balanced diet, as well as appropriate cancer screenings, especially if breast cancer has been diagnosed in the family.
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