A fatigued worker will make mistakes. A sleepy worker is less attentive and cannot react as quickly as one who is well-rested. Our bodies experience natural peaks and lulls over a twenty-four hour period, a cycle known as our circadian rhythm. The low-points affect physical activity and the ability to concentrate. Work performance is further impacted when a worker is fatigued and has lost sleep.
Naturally, the best time to work is when the circadian rhythm is high. For most people, this period is encompassed in a standard daytime work shift. However, many businesses and industries employ workers around the clock and many essential jobs need to be staffed no matter the time of day.
Shift work can be problematic, especially when it interferes with a worker's natural circadian rhythm. Even when night workers spend the same number of hours employed as their daytime cohorts, they tend to get less sleep. By necessity, they have to sleep during daylight hours when their circadian rhythm is high. Unfortunately they generally report not being able to sleep as deeply or for as many hours as nighttime sleepers. This loss of quality rest hampers performance. In many jobs, if a worker is inattentive for only a few minutes, perhaps while operating dangerous machinery or performing a delicate procedure, the consequences can be disastrous.
When scheduling shift work, some important considerations include the shift's length, the number of shifts before a rest day, rest taken between shifts, rest available during shifts, and the regularity of the schedule. Working a permanent night shift rather than rotating back to days seems like it should be beneficial as the worker adapts to night work.
However, research suggests that many workers never really get used to the schedule: they revert to a day schedule on their days off and never allow their sleep and body rhythms to adapt to being awake at night. On the other hand, workers who rotate their hours complain more frequently about their health and stress levels. When workers rotate among three shifts, some researchers recommend rotating from a day to an evening to a night shift rather than rotating from day to night to evening. This helps workers adjust to new sleep times better.
The number of hours included in the shift affects fatigue levels, not only because of the number of hours worked, but also because of the number of hours remaining for workers to attend to all of their other obligations and responsibilities in addition to getting adequate rest. Someone working 8 hours will have 16 remaining to do everything else, including sleep. Someone working 12 has only 12 remaining to accomplish the same number of tasks. Often sleep is sacrificed when other obligations require attention.
Appropriate work-rest ratios should be informed by the number and length of breaks available during the day and the number of days worked before a rest day. In many jobs, shorter more frequent breaks are ideal as are shorter periods between days off. Long strings of working days can result in cumulative fatigue that makes itself most apparent during the last shift or two before the rest day.
State and federal laws govern some aspects of work hours and overtime pay. However, these laws may not address worker stress, fatigue, or job satisfaction. Some best practices for scheduling shift work include the following:
- Avoid a permanent or non-rotating night shift. As mentioned, many workers never really get used to working at night. Also they can begin to feel isolated from management and day-shift coworkers.
- Keep consecutive night shifts to a minimum. Limiting night work between 2 and 4 consecutive days seems to limit sleep loss without being overly disruptive to the circadian rhythm.
- Avoid quick shift changes. Rotating from morning to night duty with a mere 8-hour break doesn't leave enough time for rest. At least 24 hours is ideal when rotating.
- Plan some free weekends. Being able to take one or two full weekends off per month gives workers the benefit of being able to spend time with friends and family and improves mental and emotional well-being
- Avoid several days of work followed by four- to seven-day "mini-vacations." Even though a schedule of 14 days on followed by 7 off may be popular (especially among younger workers), it also can result in high levels of cumulative fatigue on the working days and inadequate rest on the "vacation" days.
- Keep long work shifts and overtime to a minimum. Extra time at work adds to fatigue and takes away from rest time. In an ideal setting, two or three 12-hour shifts in a row should be followed by one or two rest days
- Consider different lengths for shifts. Physically or mentally demanding work can be done during shorter shifts and the lighter work should be attended to during longer shifts.
- Examine start and end times. Early start times (5 or 6 am) can disrupt even the day shift workers' sleep schedules. Ideally starting and ending times help workers avoid rush-hour traffic and are conducive to child care arrangements
- Keep the schedule regular and predictable. Regularly scheduled work results in regularly scheduled rest.
- Examine rest breaks. In some jobs standard lunch breaks are not long enough; in others, 10-minute breaks on the hour may help improve concentration and alleviate fatigue.
Not all of these recommendations are possible in every setting; however, small changes can make a big difference in improving workers' sleep, decreasing their levels of fatigue, and increasing their productivity. An alert, well-rested worker is less likely to make an error or lose concentration at a critical moment.
Note: The research noted in this article originated from Plain Language About Shiftwork,NIOSH Publication No. 97-145 .
Garrett Burnett is with the National Institute for Occupational Safety and Health.