Shiftwork schedule factors: work-rest ratios and predictability

As part of our continuing discussion of shiftwork scheduling factors, today we're talking about time on the job compared to time off. We'll also discuss the predictability of the schedule. A fixed or regularly rotating schedule may be daunting at times but an unpredictable schedule, such as those worked traditionally on the railroads takes an even greater toll.

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 worker's 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 per-son 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 before-hand. 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.”

Shiftwork schedule factors: 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 worker's 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 sup-posed 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 don't have hard and fast numbers, it seems that back-ward 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.

We'll continue this discussion of shiftwork schedule factors.

Other recent posts on shiftwork scheduling include:

• Shiftwork schedules: fixed or rotating
• Best practices for managing a shiftwork operation

Ed

Source: Plain Language About Shiftwork (NIOSH)

Shiftwork schedules in the 24/7 world

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. Good and bad points can be found in most work schedules. To determine what makes a good schedule for your operation it is important to consider a broad range of factors.

Types of Shiftwork Schedules
There are hundreds of different shiftwork schedules, also called rota. However, it is difficult to accurately count the many shiftwork schedules or rota being used. No thorough records are kept by the federal government, trade organizations, or labor unions. Different shiftwork schedules might be used by the same occupation, the same industry, or even the same workplace.

The most common shift schedule or rota 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. Off-shore oil rig workers, for example, might have a shiftwork schedule that has them work two weeks out on the rig followed by two weeks off at home.

Since so many different shiftwork schedules exist, researchers have thought of ways to measure different features of the schedules. These features are used to study how work schedules might affect safety, health, or productivity. The features are listed in Table 1 with explanations below.

Shiftwork schedule features include:

• Is the schedule permanent (a fixed schedule) or a rotating schedule?
• 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 in future posts, 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.

More on these shiftwork schedule features in future posts. We are also putting together infomration to post about shift scheduling software, which we will post with the important note that coming up with a schedule is relatively easy but coming up with a good one for your operation, and implementing it successfully require time, deliberation, and careful consideration.

Source: Plain Language About Shiftwork published (NIOSH)