Inadequate sleep causes more than $400 billion in economic losses annually in the United States and results in 1.23 million lost days of work each year, researchers have found.

The effect of chronic sleeplessness in the United States far exceeds the costs in other industrialized countries. The runner-up, Japan, loses as much as $138 billion annually to sleeplessness among workers, but that represents a greater share of its economy, researchers at the RAND Corp. found.

The number of individuals who sleep less than the recommended hours is increasing in the developed world. From 20 to 30 percent of these workers complain of a lack of sleep on a daily basis.

“Inadequate sleep is too easily accepted into the community as part of life,” said Dr. David Hillman, a clinical professor at the University of Western Australia who studies sleep deficiency. In many work settings, “sleep is an indulgence.”

On a less quantifiable level, inadequate sleep reduces the safety and productivity of workers. Researchers have linked such shattering events as the Challenger space shuttle accident to human error caused by a lack of sleep.

As the workforce becomes more competitive, he said, employers must acknowledge inadequate sleep as a threat to company productivity. Well-rested employees are more efficient, tend to be healthier and feel more content.

More people should be educated about the importance of sleep and sleep hygiene at a young age, Hillman added. Usually, poor sleeping habits in middle age can be traced back to sleep patterns formed in youth.

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