“One hour of lost sleep may not seem like a lot. But our findings suggest it could have an impact on people’s ability to stay alert on the job and prevent serious injuries,” said the article’s lead author, Christopher Barnes, Ph.D. Barnes. He and co-author David Wagner, Ph.D. were doctoral students in organizational behavior at Michigan State University when they conducted this research.
They analyzed the number of injuries reported to the Mine Safety and Health Administration (MSHA) from 1983 to 2006. The U.S. Department of Labor requires all mine operators to investigate and report all mining-related injuries. The researchers also looked at the number of workdays employees missed as a result of their injuries. Across the 24 years, there were 576,292 reported injuries on the job.
On average, 3.6 more injuries occurred on the Mondays following the switch to daylight saving time compared to other days, and 2,649 more days of work were lost as a result of those injuries. That’s approximately a 68 percent increase in lost workdays. In their analysis, the researchers controlled for weekends and holidays. Work experience did not appear to play a role in the number of injuries suffered.
More Light, Less Sleep
The researchers also confirmed that people do sleep less in the days after they’re forced to turn their clocks forward. They looked at data from the Bureau of Labor Statistics’ American Time Use Survey, which measures the amount of time Americans spend engaged in various activities, including sleep. For this study, the researchers looked at data from 14,310 interviews from 2004 to 2006. Results showed that after the switch to daylight saving time, people slept an average of 40 minutes less on the Sunday night they switched to daylight saving time.
The researchers did not, however, find any significant changes in the number and severity of workplace injuries on the Mondays after the switch to standard time in the autumn, when people gained an hour. Further analysis of the American Time Use Survey showed that people had a much easier time adjusting their sleep schedules and did not, on average, sleep less or more after they changed to standard time. These findings would help explain why there were no significant effects, according to Barnes.
The study could have some important practical implications for employers, Barnes explained.
“We think managers and organizations can use this information to help improve safety in the days following the switch to daylight saving time,” he said. “They can schedule particularly dangerous work on other days, perhaps later in the week after employees have had more time to adjust their sleep schedules.” Another suggestion would be to implement extra safety precautions on those days.
The findings were reported in the September 2009 issue of the Journal of Applied Psychology, which is published by the American Psychological Association.