"For they that sleep sleep in the night; and they that be drunken are drunken in the night.(1 Thes.5:7)

But it is true that sleeping at night and waking in the day gives me more energy. Whenever I stay awake all night until morning, I feel dehydrated and beat - something I don't feel if I sleep at night (even for just a few hours).

Humans are by nature diurnal. The body has adapted to sunlight, and people need a certain amount of sunlight. Too little sunlight can apparently cause a slight depression - seasonal affective disorder (SAD).

Human eyes are adapted to daylight, not the darkness of night.

However, some people adapt to being awake at night, and sleep during the day.

Possible the fatigue one feels in the morning corresponds with the time at which the brain would be in deep state of sleep. This would also correspond to about the time when one is dreaming. The brain needs to sleep.

Poor scheduling, combined with unhealthy attitudes about the need for sleep, can cause major problems for night workers. That’s because working at night runs counter to the body’s natural circadian rhythm, says Charmane Eastman, PhD, a physiological psychologist at Rush University in Chicago. The circadian clock is essentially a timer that lets various glands know when to release hormones and also controls mood, alertness, body temperature and other aspects of the body’s daily cycle.

Our bodies and brains evolved to relax and cool down after dark and to spring back into action come morning. People who work the night shift must combat their bodies’ natural rest period while trying to remain alert and high functioning. It doesn’t matter whether they get enough sleep during the daytime, she says. All the sleep in the world won’t make up for circadian misalignment.

That’s especially dangerous for people whose jobs require them to be on high alert and make split-second, life-or-death decisions during the night, such as medical personnel or police officers. It’s common for police departments, for example, to require rookies and lower-ranking officers to bear the brunt of night shifts. They’ll often work a few days during normal daytime hours, then either work an extra-long shift that carries on until the morning, or take a day off, rest, then work a full night shift. But that seesaw scheduling approach is a doubly bad idea, says John Violanti, PhD, an organizational psychologist who was a New York state trooper for 23 years. Not only are these highly stressful, performance-draining shifts being foisted upon the least experienced officers, but the young officers aren’t given time to adjust their sleep schedules for night work. Also, many officers seek night shifts to get overtime pay, he says. According to Vila’s research, roughly 40 percent of the nation’s 861,000 police officers work more than 12 hours a day — and a similar proportion suffer from a sleep disorder such as insomnia or excessive sleepiness.

Working against a person’s natural sleep cycle causes such sleep disorders, as well as fatigue. Fatigue, in turn, worsens moods, decreases cognitive abilities and reflexes, and makes people more vulnerable to disease, says Vila. That resulting crankiness and warped perspective can interfere with one’s ability to make sound decisions and manage people effectively, and can increase the frequency of negative encounters.

That’s not a recipe for good decisions, says Vila, especially when officers must make decisions about whether to use deadly force — often in ambiguous, fast-paced, high-risk situations. Neither is it safe for more routine activities, such as driving. "When you’re drowsy, local parts of the brain shut down for milliseconds or seconds at a time, then come back online," he says.

Night work and fatigue may also contribute to the risk of heart disease and cancer, according to research by Violanti, Vila and colleagues (Policing, Vol. 30, No. 2). Working with 98 Buffalo, N.Y., police officers, the researchers looked for metabolic syndrome — a combination of symptoms that contribute to poor heart health and diabetes, including large waist circumference, elevated triglyceride levels, high cholesterol, high blood pressure and high levels of glucose when not eating. They found that the officers who most frequently worked the 8 p.m.-to-4 a.m. shift had the highest prevalence of metabolic syndrome symptoms. Those who commonly worked that shift and also averaged fewer than six hours of sleep were four times more likely than other officers to have metabolic syndrome.

Vila and Violanti hope their findings will spur changes in shift scheduling, both for the public’s safety and the officers’.

Of course, police officers aren’t the only night-shift workers suffering from circadian misalignment. A number of studies have found that fatigue due to prolonged work hours or being called into work in the middle of the night can result in lapses in judgment and impaired motor skills among medical workers. For instance, a 2008 article in the American Journal of Surgery(Vol. 195, No. 2) reports that, when performing "surgery" on a virtual patient, well-rested surgeons were significantly smoother in their hand motions and made fewer errors than did their sleep-deprived counterparts.

Fatigue is also risky for the physicians themselves, other research has found. A 2005 report published in the New England Journal of Medicine (Vol. 352, No. 2) found that medical interns whose shifts lasted longer than 24 hours were more than twice as likely to have a car crash and five times as likely to have a driving near-miss after leaving work as interns who worked shorter shifts.

In fact, any worker who must drive while tired — whether it’s on the job or driving home after a night shift — is at risk. In 2004, the National Institute for Occupational Safety and Health reported that car crashes are the top cause of occupational fatalities, accounting for 22 percent of work-related deaths between 1992 and 2001. In 7 percent of those cases, drowsiness or falling asleep while driving was cited as a primary factor in the crash. But other factors such as driver inattention, speeding and running off the road can also be influenced by fatigue, the institute found.

Another report from 2004 found that workers across a variety of occupations who worked 12-hour night shifts were more likely than their day-shift-working colleagues to experience physical fatigue, smoke and abuse alcohol.


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