Coping with Shiftwork

Note to Readers:

 

Soon, the American Cancer Society will list shift work as a possible carcinogen.  The following article was written 3 years ago.  Prostate cancer in men has been added to the list of possible consequences of shift work.  The physiological underpinnings continue to support the notion that melatonin is a vital factor in this subject. 

 

Shiftwork and Breast Cancer – The Melatonin Connection

 

 

I almost missed the announcement on the radio while I was driving through town.  Sandwiched between the War on Terrorism and the local weather report, the bits and pieces I caught indicated that someone found a link between working nights and breast cancer.  For women who are shiftworkers, this certainly wouldn’t be good news.  After a couple of days searching the Internet, I was able to find more details, and uncovered the basis for the news bulletin. 

 

It all starts with the hormone melatonin.  At the end of a normal day, we sense the drop of light levels through our eyesight.  This triggers a reaction in the pineal gland to begin the secretion of melatonin.  As melatonin levels rise in our bodies, we tend to get sleepy.

 

Furthermore, as melatonin levels rise in women, the production of estrogen drops.  Estrogen is known as the female sex hormone.  It is believed that the production of estrogen stimulates the growth of breast tissue including some breast cancers. 

 

So to recap, more light means less melatonin, more estrogen, and greater risk of cancer.

 

In experiments in the 1970’s and 1980’s, pineal glands were removed from rats, which caused a plethora of breast cancer tumors.  And in 1991, researchers exposed rats at night to dim light, which suppressed melatonin production.  And when malignant tumors were transplanted into their bodies, they grew significantly more rapidly than in similarly treated animals kept in total darkness.

 

The next step was to test sightless women, who according to the theory should have fewer instances of breast cancer. 

 

The results of the experiments supported the theory.  Totally blind women had 60% fewer breast cancers than women of normal sight, with step-like progressions of cancer with women at various stages of partial sight.

 

Next, it was time to investigate women who worked nights.  Supposedly, women with nighttime occupations are exposed to greater durations of light.  (Night workers often sleep less during the day, and most do not sleep in total darkness)

 

In a Seattle study, researchers interviewed approximately 1600 women, half of whom worked nights.  They asked them about their work schedules, sleep habits, the amount of light in their bedrooms, past pregnancies, the use of hormones and birth control pills, smoking, and alcohol use.  They also asked about family histories of breast cancers and other factors.

 

In the findings, which prompted the current press release, women who worked night shifts were 60% at greater risk for breast cancer than women who did not.  And the greater the number of nights worked, the greater the incidences of breast cancer.

 

How do we as night workers interpret and use this data?

 

If you work nights, you are exposed to more hours of light (a combination of natural and artificial light).  This amount of artificial light you receive during your shifts may be strong enough to shut down melatonin production.  To the researchers doing the studies, interfering with melatonin production is not a trivial matter.   Dr Russel Reiter, professor of neuroendocrinology at the University of Texas Health Science Center says, “We consider the use of light too casually.  Shift work, staying up late in a well-lit environment, or turning on a bright light at night can dramatically reduce melatonin production.”

 

So what can you do?  For now, the researchers and experts are not saying to give up your night jobs – yet.  But there are some precautions to take.

 

According to Dr. Reiter, get plenty of sleep, use thick blinds to block out stray light as you sleep during the day, and if you’re a day worker and need to get up in the middle of the night for any reason, don’t turn on bright lights.

 

What about melatonin-replacement drug therapy?

 

Melatonin supplements have been used for short-term insomnia applications associated with the circadian changes of shiftwork with moderate success. 

The effectiveness of melatonin as a sleep aid for chronic insomnia however is less clear.

 

There doesn’t seem to be serious short-term effects from the use of melatonin although no systematic long-term studies have been reported.  Although melatonin is a naturally occurring substance in the human body, its ingestion in pill form has the potential to induce undesirable side effects.

 

The standards of quality regarding purity and concentration are not regulated for melatonin as they are with prescription drugs.  Therefore, I advise you to use melatonin only in concert with your doctor’s advice and oversight.

 

Sources:

 

Kathleen McAuliffe, Researchers Shine a Night Light on a Possible Link to Cancer, New York Times, June 13, 1999.

 

Susan Okie, Two Studies Link Night Work, Breast Cancer; Greater Exposure to Light Lowers Melatonin Production and Increases Estrogen Level, The Washington Post, October 17, 2001.

 

Mark Eddy, Gordon S. Walbroehl, Insomnia, American Family Physician, Aprdil 1, 1999.