Nonprofit, nonpartisan journalism. Supported by readers.

UCare generously supports MinnPost’s Second Opinion coverage; learn why.

Night work: Bad for your health

Shift work has been added to the list of risk factors for cancer, but there are other health problems you face when working nights and evenings.By Susan Perry

Shift work has been added to the list of risk factors for cancer, but there are other health problems you face when working nights and evenings.

In an article in the Dec. 7 issue of Lancet Oncology (reg. req.), the International Agency for Research on Cancer (IARC) — the cancer arm of the World Health Organization — concludes that shift work “is probably carcinogenic to humans.”

This finding marks a considerable change in medical thinking. Until now, cancer organizations have tended to slot shift work into the “uncertain, controversial or unproven” category of risk factors.

As the IARC notes, studies have found that women who work night shifts — specifically, nurses and flight attendants — are at increased risk of breast cancer. Even stronger is the evidence from animal studies. When rodents are constantly exposed to light, even dim light, or when they are put into situations that simulate chronic jet lag, they are much more likely to develop tumors.

Article continues after advertisement

Other research, not directly cited in the IARC article, has linked shift work to a higher risk of colon cancer in women and prostate cancer in men.

Nor is cancer the only health risk that increases when you work nights. A host of other ailments, such as obesity, heart disease, gastrointestinal problems (including peptic ulcers) and depression, are more common among shift workers.

About 20 percent of Americans are shift workers. Most are employed in the health care, industrial, transportation, communications and hospitality sectors of the workforce.

Disrupting the ‘night hormone’
The IARC announcement didn’t surprise Robert Sothern, PhD, a research associate at the University of Minnesota’s College of Biological Sciences and the co-author of Introducing Biological Rhythms (Springer, 2006). He’s spent an entire academic career studying the effect of disruptions in biological rhythms on human health.

Shift work, says Sothern, creates a “chronodisruption” in the body’s production of the hormone melatonin, a powerful antioxidant that, among other things, helps produce key components of the immune system, including cancer-fighting natural killer cells.

“Melatonin cues the immune system to go into high speed,” he says. And what signals the body to make melatonin? Darkness.

“When the sun’s going down, it’s a cue to the body to start making melatonin,” Sothern explains. “The problem for shift workers is when they get off the night shift, they don’t shield themselves from the sunlight.”

No darkness. No melatonin. No beneficial antioxidant activity.

Shift workers are also chronically sleep-deprived — even more so than the rest of us. As Sothern reports in his book, one study of nurses found that 80 percent of those working evening and night shifts suffered from sleep disorders compared to 23 percent of those working the day shift.

Article continues after advertisement

And as research has repeatedly shown, not getting enough sleep is a major — and often unacknowledged — health hazard.

Darkness is key
Fortunately, shift workers can take some steps (short of getting a day job) to protect their health. Here are Sothern’s suggestions:

· Fool your brain into thinking night has fallen — and into releasing melatonin — by wearing specially designed sunglasses with 100 percent protection from the sun’s blue light on your way home from work. Blue light blocks melatonin production.

· Keep a regular sleep cycle routine. Go to bed and get up at the same time each day. Make sure you get enough sleep — the amount that leaves you feeling rested.

· Keep your bedroom as dark as possible, and wear eye shades while you sleep. “Our eye lids are not opaque,” says Sothern. Light can thus suppress melatonin even when our eyes are closed.

· If your home is noisy, wear earplugs or use white noise or background music to mask sleep-disruptive sounds.

· Consider taking 1 milligram of melatonin before climbing into bed. “It helps set the body clock,” says Sothern, “and can help you fall asleep.” But talk with your doctor first. Melatonin can interact with other medications, and its long-term side effects remain unknown.