Ergonomics Research Shows Many Shift Workers May Be at Risk Of Injury

March 5, 2004
New research has determined that ergonomic issues are different for the 24 million Americans who work nights. Limited employee involvement in schedule selection, long work days and an excess of consecutive work days are all linked to increased risk of ergonomics-related injuries.

According to a new report published by Circadian Technologies Inc., poor work-life conditions and sleep deprivation can also lead to ergonomics injuries and lost workdays, especially among employees in extended hours positions (regularly working outside the hours of 7 a.m. to 7 p.m.).

"We have long known that long work hours, high fatigue levels and work schedules that fail to account for human physiological needs are linked to a 20 percent increased rate of workers' compensation claims among facilities with extended hours operations," said Kirsty Kerin, Ph.D., Circadian ergonomics specialist and one of the principal authors of "Ergonomics Risks, Myths, and Solutions for Extended Hours Operations."

The report further details the link between work practices and ergonomics injuries, such as musculoskeletal disorders (MSD). The study notes that:

In a survey of over 12,500 extended hours workers, 30 percent of male workers and 41 percent of female workers reported "chronic or frequent" back pain, while 16 percent of male workers and 27 percent of female workers reported "chronic or frequent" wrist pain.

Sleep deprivation could possibly be damaging in terms of muscle, ligament or tendon injury. With the average extended hours employee sleeping only 5.1 hours to 5.5 hours each day when working a night shift, they could face an increased risk of ergonomic injuries.

The balance of work and home life is important in controlling the number of lost work days due to MSD complaints. Both men and women who face simultaneous presence of high mental workload and increased domestic workload have increased neck and shoulder MSDs.

Disturbances in sleep affect pain and negatively impact the time it takes a worker to return to work after suffering a soft-tissue injury such as low back pain.

Six days of restricted sleep (4 hours per 24-hour period) caused changes to the sleep architecture that are similar to the changes seen in people suffering from depression. Also, lack of sleep causes changes in several natural body rhythms of hormone secretion including melatonin, cortisol, thyroid-stimulating hormone, leptin, prolactin and growth hormone.

According to Kerin, these findings raise significant new questions for managers of extended hours facilities, in which overtime levels have reached all-time highs, and in which employees regularly work evenings, nights, rotations and long shifts.

The study also challenged long-held myths on work schedules and ergonomics, clearly finding that 12-hour schedules are not inherently more dangerous for employees. With 41% of extended hours facilities using some form of 12-hour schedule in 2003, this conclusion is important to note when designing alternative work schedules. In particular, the authors found:

Although working more than eight hours a day was shown to increase ergonomic injury rates, working two to four weekends a month was also shown to have a negative impact. Since most 12-hour schedules limit consecutive workdays to four, and provide employees with twice as many weekends off as eight-hour schedules, there are pros and cons to each schedule type and 12-hour shifts are not inherently problematic.

Female risk factors for neck and shoulder ergonomic injuries include overtime and unsatisfactory leisure time, which can be linked to poorly designed schedules or excess work hours.

Employees who reported little or no influence over their work schedule had significant increases in ergonomic injuries of the shoulders, hips and knees.

Alex Kerin, Ph.D., the other study author and a Circadian ergonomics specialist, suggested managers of extended hours operations implement numerous interventions to address the increased risk of ergonomics injuries for the 24 million Americans who regularly work nights, rotating shifts, irregular and on-call schedules. "Involving employees in schedule selection, training workers on managing the work-life demands of working extended hours, and revisiting workplace policies such as break rules and rest periods can significantly decrease the risk of costly accidents and injuries," said Kerin, Ph.D.

Fatigue management initiatives to decrease employee fatigue while at work and commuting to the job, as well as improve sleep quality, also represent critical interventions for extended hours employers.

About the Author

Sandy Smith

Sandy Smith is the former content director of EHS Today, and is currently the EHSQ content & community lead at Intelex Technologies Inc. She has written about occupational safety and health and environmental issues since 1990.

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