By Nic Rowan

ADELAIDE, Australia (Reuters Health)- A 10-minute nap is better than a half-hour snooze at improving work performance, according to new Australian sleep research.

Associate Professor Leon Lack and postgraduate student Amber Tietzel studied the effect of varying nap lengths in the School of Psychology Sleep Laboratory at Flinders University in Adelaide. They conclude that 10 minutes is the most effective nap length for improving performance for up to 3 hours afterward.

"We were testing the notion of whether power naps, as they're known in the United States, are really as effective as they are claimed to be," Lack told Reuters Health. He explained that participants in the study underwent a series of performance tests and were allowed to sleep for precisely 10 or 30 minutes. Their performance level was then retested over the next hour.

"Immediately after the 10-minute nap participants showed increased alertness, both subjectively and in the performance measures, but not with the 30-minute nap," Lack said. He noted that after a 30-minute nap, participants were actually groggy for up to half an hour as a result of "sleep inertia," which occurs after longer sleeping periods.

"That surprised us a little bit," said the doctor. He explained that the team then conducted a second study, this time of performance at 3 hours after a 5-, 10-, 20- and 30-minute nap. Again, the 10-minute nap proved most successful, with the 20- and 30-minute naps producing grogginess that resulted in suppression of performance for up to half an hour after the nap.

"They are not doing any better in the first half hour than if they had no nap at all," Lack noted. "After 2 to 3 hours, the 10-minute nap is still doing better than the longer naps." The 5-minute nap resulted in some improvement in the first hour, but that dropped back to no improvement at the 2- and 3-hour mark.

"We have a chronic sleep debt, which to some extent can be repaid by a very brief nap," Lack pointed out. "For people who are in a sedentary job and trying to fight off sleepiness, it really would be smart for the employer to allow them to have a 10-minute sleep and take away those cobwebs, increase their alertness and productivity, and decrease the chances of mistakes or accidents. From a cost-benefit analysis perspective that 10-minute investment in sleep would really pay off."

Lack emphasized, however, that "the ideal solution would be to have people get enough sleep at night time."