March 17th, 2008

Study: Some Shiftwork Patterns Worse than Others for Robbing Workers of Sleep

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A new study could help employers design shifts ergonomically to reduce chronic sleep deprivation, a curse associated particularly with shiftwork. 

The National Sleep Foundation, a nonprofit organization dedicated to understanding sleep and sleep disorders, points out that shift work creates potential productivity advantages but has many inherent risks. Some of the most serious and persistent problems shift workers face are frequent sleep disturbance and associated excessive sleepiness. Sleepiness/fatigue in the work place can lead to poor concentration, absenteeism, accidents, errors, injuries, and fatalities. The issue becomes more alarming when you consider that shift workers are often employed in the most dangerous of jobs, such as firefighting, emergency medical services, law enforcement and security.

According to the International Classifications of  Sleep Disorders,  shift workers are at increased risk for a variety of chronic illnesses such as cardiovascular and gastrointestinal diseases.

The Foundation notes that managers and policy makers responsible for writing and enforcing rules regarding employee work hours must address the specific issues of a 24-hour work force in order to succeed and benefit from such a labor force. 

“Warding Off Sleepiness,” by Bruce Oliver and Jim Dillingham of Shiftwork Solutions LLC in California, breaks down shift patterns to show how adjustments can help reduce chronic sleep deprivation. The study, published in Occupational Health and Safety, is based primarily on data from their proprietary database of employee surveys conducted with more than 20,000 shiftworkers. It examines the attributes of three major shift schedule that affect employee sleep: shift length, fixed vs. rotating shifts and shift start times.

They say most managers are aware that shiftworkers don’t sleep as well as other employees, but few understand how their organizations’ shift schedules contribute to the problem.

Comparing the survey results of people working eight-hour shifts with those working 12-hour shifts, they found that the length of the shift affects the amount of sleep shiftworkers get. Over a span of several days or weeks 12-hour shifts provide twice as many days off, and employees sleep longer on their days off. Regardless of whether the comparison is between people working day shifts only, night shifts only, or a rotating shift schedule, the average hours of sleep during the four-week period is greater for 12-hour shiftworkers.

Comparing rotating shifts with fixed or “steady” shifts, they found that people working a rotating schedule average roughly the same amount of sleep during a four-week period as people working a fixed night shift schedule, but they get less sleep than people working a fixed day shift or fixed afternoon shift.

Fixed shifts allow shiftworkers to sleep at approximately the same time each day, according to the authors, which avoids the physical stress (and poor-quality sleep) most people experience when they adjust their circadian rhythm to a new sleep period with each rotation. This benefit is realized by those working fixed day, evening, and voluntary night shifts. They saw the benefits undermined, however, when workers on a fixed night shift adopted a daytime routine during their days off work.

Studying the impact of shift patterns at a large auto plant, the authors looked at differences between workers who began at 6:30 a.m. to those who began an hour later.

In line with results reported by The National Institute for Occupational Safety and Health (NIOSH) and the Finnish Institute of Occupational Health, the survey showed a one-hour delay in morning shift start times increased worker sleep and improved waking alertness during the shift. The authors  concluded sleep was truncated when workers have early start times because of family and social activities in the evenings. They found the evening and night shifts were affected negatively by starting work later; however, the results were less consistent across all measures.

Source: National Sleep Foundation; Occupational Health and Safety

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