Safer Shift Work through More Effective Scheduling

Sleep patterns, rest breaks, 'mini-vacations,' are all part of the equation.

• By George Brogmus, Wayne Maynard
• Dec 01, 2006

SO many industries utilize shift work schedules that nearly 15 million full-time workers in the United States work shifts outside the traditional 9-to-5 or flextime workday, according to the Bureau of Labor Statistics. Yet those added shifts, implemented specifically to increase profitability, may actually be costing companies money through higher worker injury rates. By rethinking how you schedule shift work, you can help keep workers safe and make each shift more effective.

Based on the findings of a recently published Liberty Mutual Research Institute study modeling the impact of the components of long work hours on injuries and accidents, the loss prevention group developed a program to assess worker injury risk based on work scheduling factors such as time of day, hours per shift, number of consecutive shifts, and time between rest breaks. The program addresses the following shift work problems:

• Work-related injuries increased 15.2 percent on afternoon shifts and 27.9 percent on the night shift relative to the morning shift.
• Injury risk increases nearly linearly after the eighth hour of a shift, with risk increasing 13 percent on a 10-hour shift and almost 30 percent on a 12-hour shift.
• As consecutive shifts increase, injury risk also increases, but at a higher rate for night shifts than for day shifts:
  **Average risk for injury is 36 percent higher on the last night of a four-consecutive-nights shift. Risk increases incrementally over each night on the job: 6 percent higher on the second night, 17 percent higher on the third night, culminating at 36 percent on the fourth night.
  **Injury risk is 2 percent higher on the second morning/day shift, 7 percent higher on the third day, and 17 percent higher on the fourth day than it is on the first shift.
• Injury risk also increases as time between breaks increases. The last 30 minutes of a two-hour work period has twice the risk of injury of the 30 minutes immediately after the break.

One way to combat these problems is to evaluate the combined effect of work scheduling factors rather than to just limit total work hours. For example, scheduling four 12-hour day shifts with hourly breaks will produce less risk than six eight-hour night shifts with hourly breaks. Both shift schedules add eight hours of work, but only one has significantly less risk of injury.

If you are contemplating adding overtime or expanding shifts, consider the following guidelines to help build a safer shift work schedule. Tips for general shift work:

• Establish maximum limits for days and nights worked per week, including overtime.
• Favor day/morning shifts over afternoon or night shifts.
• Consider adding hours to existing shifts or add an additional day of work to the project.
• Limit work to five or six consecutive shifts.
• Provide for frequent rest breaks. Hourly breaks are generally appropriate, but consider providing more frequent breaks for highly repetitive or strenuous work.
• Schedule work so every worker has at least two consecutive rest days and that at least one of these days is Saturday or Sunday.
• Avoid scheduling several days of work followed by four- to seven-day mini-vacations. These schedules should be used only when there is no other choice (such as in mining or oil exploration).
• Keep schedules regular and predictable.
• Alternate weeks of overtime with weeks of normal time.

Get Workers Involved
For those situations when you have to schedule night shifts, here are some ways to help combat the increased risk of injury:

• Keep consecutive nights shifts to a minimum: Four nights maximum in a row should be worked before a couple of days off, and schedule no more than 48 hours of night shift work per worker per week.
• Educate workers on the importance of getting enough good sleep. Suggest they use blackout drapes, turn off phone and pagers, and use a fan or white noise to mask daytime noises. Regular exercise, diet, and relaxation techniques are also effective strategies for coping with night work.
• Consider alternatives to adopting permanent night shifts. Most workers never fully adapt to night shift work because they go back to a daytime schedule during days off.
• Avoid quick shift changes, and adjust shift length to the workload.
• Take into account all aspects of workers' jobs and home lives when changing work schedules.

When scheduling shift rotation, provide a minimum of 11 hours off between shifts and a minimum of 24-48 hours when rotating workers off the night shift. Ideally, the change from the night and morning shifts should happen between 7 a.m. and 9 a.m. because starting the morning shift too early often cuts down on evening sleep time. Also, keep in mind that forward shift rotation--going from a day to afternoon, or afternoon to night, or night to day shift--is more compatible with normal sleep patterns than backward shift rotation.

Whatever approach you take to scheduling shift work, a very important component is worker involvement. You should solicit worker feedback in the scheduling process rather than handing down a mandatory schedule. And provide training or awareness programs for new shift workers and their families to help them cope with the irregular schedule. Lastly, ensure that workers on all shifts, including the non-traditional schedules, have access to health care and counseling services.

With 15 percent of the total full-time U.S. workforce working non-traditional shifts, rethinking shift scheduling can make a significant impact on productivity and worker safety.

This column appeared in the December 2006 issue of Occupational Health & Safety.

This article originally appeared in the December 2006 issue of Occupational Health & Safety.