Is The Night Shift Bad For Your Breasts?

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.

Image credit: Thinkstock.


Jose L.
Jose L.4 years ago


> If you have breast cancer in progress, the addition of vitamin D can help stop cancer cells in their tracks by replenishing E-cadherin. Once cancer growth is slowed, your immune system can begin to get ahead of the cancer cells, because it doesn’t have to deal with gazillions of them. It’s just disposing of the “leftovers.” The theory above is Dr. Garland’s DINOMIT theory and has been substantiated by subsequent studies by other researchers.

I quoted enough that I feel obliged to mention this may or may not be fair use and the article is "copyright 1997-2013 Dr. Joseph Mercola. All Rights Reserved."

Jose L.
Jose L.4 years ago


> Dr. Cedric F. Garland of the University of California's San Diego Moores Cancer Center is the epidemiologist who has connected the dots between Vitamin D deficiency and cancer. According to Garland, in nearly all forms of breast cancer, vitamin D affects the structure of your epithelial cells. These cells are held together by a glue-like substance called E-cadherin, which provides structure to the cell. E-cadherin is made up of mostly vitamin D and calcium.

> If you don’t have adequate vitamin D, that structure comes apart and those cells do what they are programmed to do in order to survive — they go forth and multiply. If this growth process (cell proliferation) gets out of control, you may end up with cancer.

Jose L.
Jose L.4 years ago

From a mercola article:

> Vitamin D has powerful effects when it comes to breast cancer, to the degree that breast cancer is being described as a “vitamin D deficiency syndrome.” Of course, other lifestyle factors are also important in preventing cancer, such as nutrition, exercise, sleep, and managing stress. However, vitamin D’s critical importance seems to grow with every emerging study.

> Carole [Baggerly of GrassrootsHealth] believes that 90 percent of ordinary breast cancer is related to vitamin D deficiency — which is 100 percent preventable!

> This is absolutely a profoundly important statement. As breast cancer is the most common cancer in women, this has massive implications for women’s health.

Jose L.
Jose L.4 years ago

There are many possibilities, but why didn't they consider or mention Vitamin D?

I work at nights, and it's not that uncommon to find yourself entirely indoors during the day for weeks at a time, so you miss out on the sun (especially the mid day sun). You pick up groceries and what not when it is dark or too early to get UVB. And yes I did start to suffer and solved part of my problem (fron an injury) with Vitamin D supplements.

So it makes sense that over many years, especially once your kids/grandkids have left the house and you have few reasons to go out during the day, that you would tend to avoid a lot of sunlight. Add that older folks' skin does not make vitamin D as easily and that Canada has a high latitude. Add that in older age after work you want to rest.

And, of course, a shortage of Vitamin D does increase your chances of getting breast cancer significantly.

Stacey Toda
Stacey Toda4 years ago

Interesting but not too sure I believe it. You can work the night shift and still be out during the day

federico bortoletto
federico b4 years ago

Grazie per le notizie ma sono alquanto scettico.

Eternal Gardener
Eternal G4 years ago

? I'd say plastic surgery is the #1 threat to breasts...

Grace Adams
Grace Adams4 years ago

I have heard this several times before--it seems melatonin is a strong antioxidant that really helps breasts--you can buy melatonin supplements, even 10 mg triple strength melatonin capsules--so maybe night shift workers should try melatonin when they dry to sleep in the day time along with darkening their bedroom--both to get more sleep and as an anti-oxidant to protect their breasts.

Sandi C.
Sandi C4 years ago

I know age does

Cathleen K.
Cathleen K4 years ago

Yikes! I'm a nurse and worked nights for about 15 years - it pays more, in case you were wondering, and you also have a lot more autonomy. As an L&D nurse, I liked managing the entire labor process myself and just waking the doctor when it was show time - you're less likely to end up in the OR that way.