Types of Night Shifts and Their Effects on Workers

Shiftwork experts often are asked what is the best or worst work schedule. There is no simple answer to this question because there is no ideal schedule that fits every situation. Both good and bad points can be found in most work schedules. In this section, we suggest ways to examine work schedules to identify their advantages and disadvantages. There are hundreds of different shiftwork schedules. However, it is difficult to accurately count the many shiftwork schedules being used. No thorough records are kept by the federal government, trade organizations, or labor unions. Different schedules might be used by the same occupation, the same industry, or even the same workplace. The most common shift schedule probably is five days on a single shift followed by two days off. If this is a rotating shift schedule, the worker will change to a new shift after the days off. Depending on the job, it is even possible to work 7, 10, or 14 days in a row. Offshore oil rig workers, for example, might work two weeks out on the rig followed by two weeks off at home.

Schedule Features

We already have mentioned the time of the shift and whether shifts are permanent (fixed) or rotating. It also is important to consider: How long a shift might be. How many shifts are worked before a rest day. How many rest days are on weekends. Whether there is overtime. How much rest is taken between shifts. How much rest is taken during the shift. Whether the work schedule is regular and predictable. As we will explain, all of these features can affect the amount of stress and fatigue a person feels because of the work schedule. If people experience too much stress and fatigue, then they might not do their jobs safely and efficiently. Or they might develop health problems. Here are some particulars about the different shift features: Time of Shift: Twenty-four hour operations usually are divided into two or three shifts. Start- and end-times depend on the length of the shift. Day shift (also called morning or first shift) starts around 5 to 8 a.m. and ends around 2 to 6 p.m. Evening shift (also called afternoon or second shift) starts around 2 to 6 p.m. and ends around 10 p.m. to 2 a.m. Night shift (also called third, "graveyard, or "mid shift) starts around 10 p.m. to 2 a.m. and ends around 5 to 8 a.m. Why is the time of shift important?

Because people who work in the late night or early morning hours often feel sleepy and fatigued during their shift. This happens because their body rhythm (also called a circadian rhythm) tells them to be asleep at those times. Night workers also must sleep during the day, when their circadian rhythm tells them to be awake. Because of this, day sleep is short and feels "light or unsatisfying. Often, night workers dont get enough sleep during the day to combat nighttime fatigue and sleepiness. Also, day workers sometimes must wake up very early to go to work. This might cause them to cut off their sleep, which makes them feel tired during the day. Shift times also determine when a worker can see family and friends. Many social events take place in the evening, which means they might be missed by evening or night workers. Parents who work the evening shift might not see their children during the week because they are at work when the kids return from school. If this happens too often, it can be stressful.

Permanent versus Rotating Schedules

We might think that permanent night workers adapt or get used to their work times. Usually, the longer somebody does something, the easier it becomes. With experience, many night workers figure out tricks or personal methods to fight off some of the nighttime fatigue. However, research tells us that most permanent night workers never really get used to the schedule. That is, there are many nights when they still feel tired and sleepy. Fatigue occurs because most night workers go back to a day schedule on their days off. This is not surprising because family and friends are active during the day. Also, many errands and chores (like getting the car fixed) must be done during the day. Because most night workers often return to a day schedule, they never completely allow their sleep and body rhythms to adapt to being awake at night. They also sleep less during the day, so they dont recover from fatigue. This fatigue can carry over from day to day. Over several days, fatigue can accumulate to unsafe levels. People working rotating schedules face a similar situation. Because the shift times are always changing, they can never completely adapt to a set work schedule. Rotating schedules are often used because they are considered fairer to all workers. Everybody in the workforce takes their turn at both the popular and unpopular shifts. Rotating shiftworkers are always trying to get used to changing work times. This is not easy, which is why rotating shiftworkers have more complaints than other workers about physical health and psychological stress. Research has shown that rotating shifts have special features that might affect a persons ability to get used to the schedule. These features are explained below.

Speed and Direction of Rotation

Adapting to rotating shifts can be affected by the speed of rotation and the direction of rotation. Speed of rotation means the number of consecutive day, evening, or night shifts before a shift change occurs. Direction of rotation means the order of shift change: A forward rotation is in the clockwise direction, from day to evening to night shift. A backward rotation is in the counterclockwise direction, from day to night to evening shift. Different rotation speeds also affect a workers ability to get used to change of shift times. We have already talked about the same situation under permanent versus rotating shifts. Longer rotations (for example, three to four weeks of working the same hours) are supposed to allow workers more time to get used to night shifts. However, workers usually return to a day schedule on their days off. A fast rotation (every two days, for example) allows no time to get used to night work. Some researchers prefer the fast rotation, because the worker quickly gets through the tough shifts and then has a couple of days off. Very fast rotations are used in Europe more than in America. Direction of rotation can affect the ability of circadian (daily body) rhythms to adapt to the change in work times. Sleep, for example, is a circadian rhythm because each person sleeps for part of every day. Some researchers suggest that a forward, or clockwise, rotation is better for helping a worker adjust to new sleep times. This suggestion was made because it is easier to go to bed later and wake up later than earlier. Our body rhythms make us feel more awake and alert in the early evening. This makes it harder to fall asleep earlier. Backward rotations work against the body rhythm by forcing the worker to go to sleep earlier and earlier. Although we dont have hard and fast numbers, it seems that backward rotation schedules are used frequently in the United States. It is not completely clear why. It is partly because of custom (We always did it this way) and partly because workers like the "long change. In the long change, workers pick up an extra day off when going to evening shifts after night shifts. This happens because evening shift starts late in the day, which leaves most of that day free for non-work activities.

Work-Rest Ratios (or How Much Work Before a Rest)

The more a person works, the less time he or she will have for rest. People who work an 8-hour shift will have 16 hours left in a day to do everything else, and also to get some rest. People who work a 12-hour shift have only 12 hours to do everything else and to rest. In a situation like this, the extra work hours mean more tiredness and less time for rest. This is a two-edged sword. For example, many times a workers home responsibilities, such as taking care of children, cannot change from day to day. So, if workers do overtime or a 12-hour shift, they still must take care of home duties. Since these duties take the same amount of time every day, workers may sacrifice rest and sleep after a long workday. This example shows us how important the length of shift can be in terms of stress and fatigue. When looking at work versus rest, we also must consider how many breaks are taken during the shift and the length of breaks. Depending on the type of work and length of the day, several short breaks might be better than a few long breaks. Short breaks might be better particularly for jobs requiring heavy physical labor. How tired a worker is also depends partly on how many days in a row he or she works. Fatigue builds up over several workdays, as well as over a single workday. This happens especially when a person gets less sleep between workdays than on rest days. As we mentioned earlier, a worker might not get enough sleep between long workdays because of home responsibilities. So, if a person works several days in a row, for example, six or seven, a good deal of sleep might be lost. Then the worker feels quite tired during the last one or two shifts.

How Regular or Predictable?

Most jobs have a very regular, set schedule. A worker usually knows the schedule ahead of time. Even if the shift times change, a worker will know several days beforehand. This makes it easy to schedule other non-work activities, such as making sure somebody is at home when the children get there. Other jobs are not so regular or predictable. For example, health care workers might respond to emergencies that keep them on the job much longer than expected. Or, they might be on call for such emergencies. At a factory, a breakdown or a last-minute call for a product might keep workers at the plant working overtime. Railroad workers sometimes work off a "call board. This means they can be assigned to a train at the last minute to move a "just-in-time order of goods. If workers cannot predict their schedules, it is difficult to get adequate rest. Maybe they just get to sleep when they are called back to work, or maybe they have just worked a long shift when an emergency happens. So, they stay at work a few more hours. Maybe they are on call and never get deep, satisfying sleep because they are always listening for the phone. Some people call this "sleeping with one eye open.

Credit for this article goes to: Plain Language About Shiftwork Roger R. Rosa 1 Michael J. Colligan 2 U.S. DEPARTMENT OF HEALTH AND HUMANSERVICES