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Keep It Dark At Night
Drs Neal Barry and Nicole Barry

Recent research has shown that altering your sleep cycles negatively influences hormone release and may raise your risk for cancer.  Read on to find out your doctors’ orders.

Men who rotate between daytime and nighttime shifts on their job have triple the normal rate of prostate cancer according to a study that followed 14,000 men in Japan since the late 1980’s.(1)  Previous research had linked breast cancer in women to night shift work but this is the first clear evidence that a rotating work schedule increases the cancer risk for men.

In the study on men, nighttime only workers did not have significantly different cancer rates from daytime only workers.  But rotating shift workers had three times the incidence of daytime workers.  In previous research, women who worked the night shift had 50% greater risk of breast cancer than other working women.(2)  Researchers suspect that the hormone melatonin protects against prostate and breast cancer, and research has already shown it slows the growth of breast tumors.  Melatonin levels go up and down in our bodies in a daily rhythm regulated by light exposure with melatonin being produced during dark periods.  Remarking on the studies of women one researcher said, “Light at night is now clearly a risk factor for breast cancer.”(3)  It may be that the women who worked night shifts did not sleep in total darkness in the day and so melatonin levels never rose high enough to be protective.  But if a night worker has regular exposure to darkness the melatonin rhythm reverses.  Rotating shift workers don’t seem to get a chance to adjust and so their melatonin levels stay suppressed.

Current research is underway to see if melatonin supplements could fight prostate cancer or protect workers on rotating shift but the jury is still out on those issues.  Meanwhile, Drs. Barry & Olsen recommend working consistent hours, rather than rotating and working late at home; and if you do work at night, make sure that your bedroom is totally dark when you sleep.  Drs. Barry & Olsen suggest even daytime workers would do well to insure they sleep in near darkness, avoiding nightlights in the bedroom and using opaque blinds or shades in urban areas where street lights can add too much light to the room.  Some even suggest you not turn on bright bathroom lights on trips in the night to the bathroom, but instead to just use a nightlight in the bathroom.

  1. American Journal of Epidemiology, September 15, 2006 (as reported by B. Harder, “Graveyard Shift,” September 23, 2006, Science News, Vol. 170, No. 13, p. 195).
  2. July 20, 2005, Journal of the National Cancer Institute, (as reported by B. Harder, “Bright Lights, Big Cancer,” January 7, 2006, Science News, Vol. 169, No. 1, p. 8).
  3. D. Blask of the Bassett Research Institute in Cooperstown, NY (as reported by B. Harder, Ibid.).

In This Issue:
Keep it Dark at Night
Down Syndrome Test Urged for Pregnant Women
Antibiotics Not Needed for Runny Nose
Recipe: Tomato Soup

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