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Using data from the Mine Safety and Health Administration, researchers found that workplace accidents increase as clocks jump ahead and employees lose an hour of sleep beginning on the second Sunday of each March. On the other hand, the study found no significant increase in workplace accidents or sleep loss when the clocks were set back an hour in November.

In two separate studies, Christopher Barnes and David Wagner, both doctoral candidates studying industrial and organizational psychology at the university, found that the March switch resulted in 40 minutes less sleep for American workers, a 5.7 percent increase in workplace injuries, and nearly 68 percent more workdays lost to injuries. The study, which will be published in the Journal of Applied Psychology, concluded that losing the hour of sleep can make a significant difference for employees engaged in jobs requiring a high level of attention to detail.

Some industries, like trucking and airlines, have recognized this factor and have implemented regulations setting limits on the consecutive hours that employees can drive or crews fly without taking a break.

The researchers said other studies support their findings. A study using information from the National Highway Traffic Safety Administration cited sleep deprivation as the most likely cause of a 17 percent increase in accidents on the Monday after the time change. A University of British Columbia study using data from the Canadian Ministry of Transport found that when Canada went into daylight savings time, there was an 8 percent increase risk of accidents on the Monday after the changeover.

Internal clocks need to adjust. Barnes pointed out that is not uncommon for people to complain how tired they are when they lose sleep. Many people adjust to a pace where events occur regularly and they can be adversely affected when that schedule is disrupted. An obvious example is jet lag, which occurs when people travel across several time zones.

"Their internal clocks need some recovery time for these kinds of disruptions," Wagner said.

Barnes noted that employees assume the change to daylight savings is not going to greatly affect them because, after all, it's only one hour. If they do have an accident or make a mistake, he said, they are also not likely to attribute it to sleep loss. However, researchers said the results clearly show that sleep does have a profound effect on human behavior and lack of sleep can have significant and serious results.

June 22, 2009

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