Article written by George Brogmus and Wayne Maynard 4 October 2006
Findings of a recently published Liberty Mutual Research Institute study modeling the impact of the components of long work hours on injuries and accidents:
* 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-night 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 2-hour work period has twice the risk of injury as the 30 minutes immediately after the break.
Advice to minimise problems includes:
* Evaluate the combined effect of work scheduling factors rather than to just limit total work hours (i.e. time of day, breaks on shift).
* Establish maximum limits for days and nights worked per week, including overtime. Whenever possible, 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, and limit work to five or six consecutive shifts.
* Provide for frequent rest breaks. Hourly breaks generally are 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 at least one of these days is Saturday or Sunday.
* Avoid scheduling several days of work followed by four- to seven-day mini-vacations.
* 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 shiftwork per worker per week.
* Educate workers on the importance of getting enough good sleep. Suggest they use black-out drapes, turn off phones and pagers and use a fan or white noise to mask daytime noises. Regular exercise, diet and relaxation techniques also are effective strategies for coping with night work.
* Consider alternatives to adopting permanent night shifts. Most workers never fully adapt to night shiftwork, since 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' job and home lives when changing work schedules.
* Provide a minimum of 11 hours off between shifts and a minimum of 24 to 48 hours when rotating workers off the night shift.
* Change from the night and morning shifts should happen between 7 a.m and 9 a.m., as starting the morning shift too early often cuts down on evening sleep time.
* 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.