When we think of “shift work,” we most often think of the overnight shift – one that starts at night and ends in the morning, but in fact there are many variations of this, and what it really means is work hours that do not include or stick to a straight Monday to Friday and 9 to 5 rotation. Still, it’s the night shift itself that causes the most impact on us, and on those we live and interact with.
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Since the discovery of the light bulb, where we could illuminate our work places, hours of work have increased and become more varied as industry kept pace with the demand for consumer goods. An added result of this increased activity was the need for services (transit, food, gas) to support these “off time” workers. An increase in night time activity also means that EMTs, Police, Fire, Nurses, Doctors, (etc.) need to be available. You want that package tomorrow? Someone’s got to move it for you. Even when we’re in the middle of the dark hours of a night shift, it seems there’s not much happening out there and it feels as if this night will never end, it’s little comfort that there are actually millions of us experiencing this very same thing.

Working nights goes against our body’s natural need to rest when it’s dark and wake when it’s light and when we do this it almost always causes sleep deprivation and fatigue. Our internal body clock spontaneously generates a circadian rhythm that regulates many processes such as temperature control, hormone production, alertness, and sleep. It runs on a time frame of approximately 24 hours and is strongly influenced by the earth’s light and dark cycles. Basically, no matter how good you get at working nights, we’re still fighting nature.
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In general we need one hour of sleep for every two that we’re awake, so about 8-9 hours a night. Shift workers tend to have poor sleep quality that is fragmented, resulting in a sleep debt – one that adds up and can only be helped if we repay that debt as soon as possible. …And that’s not very likely is it?

David Ballard, Director of the Center for Organizational Excellence and Psychologically Healthy Workplace Program at the American Psychological Association says, “The body gets confused. Lack of sleep causes great stress in night shift workers. When you work at night, you're cut off from friends and family, you have little social support, your diet may not be as healthy. When day shift workers get home, we do things that relax us, like go out to eat or grab a drink with a friend. But when you're working the night shift, you lose that. You're facing additional stress, but you have fewer ways to cope with it."

The long-term physical health effects associated with working nights are well documented. In 2007, shift work was listed by the World Health Organization's International Agency for Research on Cancer as a "probable carcinogen." Researchers from the Fred Hutchinson Cancer Research Center in Seattle found that women who work the night shift have a 49 percent increased risk of being diagnosed with early-stage ovarian cancer. While no one is sure of the cause, it's thought that suppressed levels of the hormone melatonin put workers at risk. Melatonin production usually occurs at night and is compromised under artificial light. Melatonin in turn regulates pituitary and ovarian hormones including estrogen. Elevated levels of estrogen are linked to increased risk of reproductive cancers. A 2012 study in the American Journal of Epidemiology reported that men who work at night are three times as likely to develop prostate cancer as are day workers. The ongoing disruption of a person's natural circadian rhythms has also been linked to cardiovascular disease, obesity, digestive problems, and diabetes. One study showed that night shift work contributed to higher rates of heart disease among police officers. Nighttime truck drivers had higher rates of hypertension as well as heart disease.

Physician Alon Avidan, director of the UCLA Sleep Center, says it's not uncommon for shift workers to develop psychiatric conditions due to accumulated sleep debt. "Things get to a point where it begins to impact their social function and relationships. They might feel depressed or more anxious. We'll see relationships break up or moms or dads not able to fulfill their obligations as parents," he says.

Shift workers report that it's their day-to-day life that suffers most, especially since society is built around a 9-to-5 work schedule. You can't go to a medical checkup at nine at night or call an electrician at two in the morning when you're on break. You miss out on barbecues and christenings, school plays and lunch dates. If your boss works days, you may not see him for weeks. You're certainly not in a book club. "Night shift workers begin to feel like second-class citizens," says Carole Lieberman, a psychiatrist on the clinical faculty at UCLA's Neuropsychiatric Institute, who has treated shift workers. "They begin to feel invisible."

Many night workers are diagnosed with Shift Work Disorder, a diagnosis given to anyone who cannot cope with the changes in their circadian rhythm. They experience extreme sleepiness, and often insomnia and depression as well. According to Avidan, individuals with Shift Work Disorder are three times more likely to have an accident on the job than are employees who do not work a night shift. Even if they think they're sleeping enough during the day, they may not be getting the sleep they need. Many shift workers get off in the morning, take a one-hour nap to take the "edge" off, then wake up to make breakfast and drive the kids to school. "Maybe they go back to sleep at 10 or 11 A.M., but now their sleep is fragmented," says Avidan. "Sleep has to be taken in one chunk. It's like baking a cake. Instead of leaving it in for an hour, you leave it in for five minutes at a time. Well, then it's never going to bake. When shift workers take a nap and then go back to sleep later, they're not getting the restorative sleep they need to feel recovered." Actually, they may not feel recovered at all unless they stop working the night shift, which is what Avidan always suggests as the first step in treatment.

Accumulated sleep debt takes a toll on an individual's ability to make good decisions, let alone sharp, split-second ones required of nighttime workers in life-and-death situations. Major accidents like the Exxon Valdez oil spill, Three Mile Island, and the meltdown at Chernobyl took place during the night shift. But being on the night shift doesn't just influence reaction times—it changes how we react in challenging situations: One study found that police officers who work the night shift are angrier and more hostile to people they pull over than are daytime officers.
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The night shift takes a toll on marriages. Research shows that night shift workers' divorce rates are higher and they report less marital satisfaction than other workers. With one spouse getting home just as the other leaves for work, husbands and wives are less physically and emotionally available to each other. On weekends, the spouse working the night shift tries to catch up on sleep rather than taking the kids to the movies or to the park. And forget chores: Night shift workers report putting off household duties, even those as simple as laundry, because they're fatigued. Often, one partner will begin to feel the division of labor is unequal, and resentment builds.

Research shows that we, as shift workers are less likely to interact with society in general – less likely to talk to neighbors, go out to restaurants, shows, and or sporting events – probably we’re just getting ready for work. It’s really not much fun to go places with people having a good old time when all you can think of is what you can’t do (like have a drink) and when you have to leave to get to work on time. We either hang out with our night shift co-workers, or we don’t really hang out at all… very often.

Still there are benefits to working nights and different shift rotations. It can leave you available to volunteer at your children’s schools, skip the Monday to Friday commute, stay up really really late some nights and stay in bed the next morning, or do groceries when it’s just you and the retirees in the dairy aisle and you could shoot a cannon down the checkout lane.

Is it all bad? Not at all. Am I switching to straight days? Not if I can help it. Can you get used to it? Shift your circadian rhythms to suit your work? Anything’s possible I suppose but whenever I’m asked, “Aren’t you used to it by now?” My answer will always be, “No, but I am used to being tired.”

Portions excerpted from “The Night Shift”, by Brooke Lea Foster
Published in Psychology Today . You may read the full article here