The graveyard shift and cancer

By Tom Fortner • Published: March 10th, 2008
Category: Health in a Heartbeat

No one is quite sure how the graveyard shift got its morbid name. The term, which describes the working hours from around midnight to daybreak, may hail from the days when police patrolled cemeteries to guard their silent occupants from grave robbers. Or the name may generally refer to the “ghostlike hour of employment.”

It could turn out that the graveyard shift deserves its distinctive name for another, more serious reason. The World Health Organization recently classified late-shift work as a possible cause of cancer.

Don’t be overly alarmed. The new designation simply means a link between night work and cancer is plausible, but the evidence isn’t definitive and there may be other explanations for increased incidence of cancer in late-shift workers.

That higher incidence has been documented by studies showing that women who work the third shift are more prone to breast cancer. Some evidence also points to increased risk of prostate cancer in men.

What could be the cause? The graveyard shift may disrupt the circadian rhythm… the cycle of wakefulness and sleep. Melatonin [mel-ah-toe-nin], a hormone known to suppress tumors, is mainly produced at night and its development is inhibited by light. Another theory holds that people who work the late shift are chronically tired, and their weakened immune systems leave them vulnerable.

As many as one-fifth of employees in developed countries work the graveyard shift. As researchers wake up to its possible ill effects, millions of people will be interested in knowing what they find out.