As featured in American Police Beat
By Mark Nichols
A startling medical report with great implications for law enforcement officers makes a strong case that people who work through the night or the “graveyard shift” have a higher risk of developing certain kinds of cancer. The findings are based on research that discovered higher rates of breast and prostate cancer among people who go to work when everyone else is home sleeping. The higher cancer rates don’t prove working overnight can cause cancer – there may be other factors common among graveyard shift workers that raise their risk for cancer.
However, the findings are strong enough that next month, the International Agency for Research on Cancer (the cancer arm of the World Health Organization) will add overnight shift work as a probable carcinogen. Scientists suspect that overnight work is dangerous because it disrupts the circadian rhythm, the body’s biological clock, according to Maria Cheng, a reporter with the Associated Press. The hormone melatonin, which can suppress tumor development, is normally produced at night. If the graveyard shift theory eventually proves correct, millions of people worldwide could be affected.
Experts estimate that nearly 20 per cent of the working population in developed countries work night shifts. Cheng reports that among the first to spot the night shift-cancer connection was Richard Stevens, a cancer epidemiologist and professor at the University of Connecticut Health Center. In 1987, Stevens published a paper suggesting a link between light at night and breast cancer. Back then, he was trying to figure out why breast cancer incidence suddenly shot up starting in the 1930s in industrialized societies, where nighttime work was considered a hallmark of progress.
Most scientists were bewildered by his proposal. But in recent years, several studies have found that women working at night over many years were indeed more prone to breast cancer. Also, animals that have their light-dark schedules switched develop more cancerous tumors and die earlier. Some research also suggests that men working at night may have a higher rate of prostate cancer. The studies mostly focused on nurses and airline crews and many scientists say more studies among other professions have to be conducted before the findings are considered conclusive.
There are many people out there who doubt the results. They point out that the “probable carcinogen” tag means that the link between overnight work and cancer is merely plausible and that the list of “known” carcinogens is huge and includes things like alcoholic beverages and birth control pills. Scientists believe having lower melatonin levels can raise the risk of developing cancer. Light shuts down melatonin production, so people working in artificial light at night may have lower melatonin levels. Melatonin can be taken as a supplement, but experts don’t recommend it long-term, since that could ruin the body’s ability to produce it naturally. Sleep deprivation may be another factor in cancer risk.
People who work at night are not usually able to completely reverse their day and night cycles. “Night shift people tend to be day shift people who are trying to stay awake at night,” said Mark Rea, director of the Light Research Center at Rensselaer Polytechnic Institute in New York, who is not connected with the IARC analysis. “Not getting enough sleep makes your immune system vulnerable to attack, and less able to fight off potentially cancerous cells,” he said. Confusing your body’s natural rhythm can also lead to a breakdown of other essential tasks. “Timing is very important,” Rea said.
Certain processes like cell division and DNA repair happen at regular times. Even worse than working an overnight shift is flipping between daytime and overnight work. List of known and probable carcinogens from IARC and National Toxicology Program listed on American Cancer Society website: http://tinyurl.com/2kl5ab. Or check out the International Agency for Research on Cancer’s website at: http://www.iarc.fr./
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