Short naps don’t restore the damage of a sleepless night

EAST LANSING, Mich. — Napping during the day can feel like a quick way catch up on your sleep, but a new study reveals that quick a “power nap” isn’t really supplying much power. In fact, a team from Michigan State University says napping for 30 to 60 minutes does little to restore the damage of a sleepless night.

“We are interested in understanding cognitive deficits associated with sleep deprivation. In this study, we wanted to know if a short nap during the deprivation period would mitigate these deficits,” explains Kimberly Fenn, director of MSU’s Sleep and Learning Lab, in a university release. “We found that short naps of 30 or 60 minutes did not show any measurable effects.”

“While short naps didn’t show measurable effects on relieving the effects of sleep deprivation, we found that the amount of slow-wave sleep that participants obtained during the nap was related to reduced impairments associated with sleep deprivation.”

Slow-wave sleep is vital for your health

Slow-wave sleep (SWS) is the deepest and most rejuvenating level of sleep a person reaches. During this time, scientists detect high amplitude, low frequency brain waves coming from people. Their bodies are also the most relaxed and their heart rates reach their slowest point during SWS.

“SWS is the most important stage of sleep,” Fenn says. “When someone goes without sleep for a period of time, even just during the day, they build up a need for sleep; in particular, they build up a need for SWS. When individuals go to sleep each night, they will soon enter into SWS and spend a substantial amount of time in this stage.”

Every minute of slow-wave sleep helps the body

Researchers recruited 275 young adults to take part in a series of cognitive tasks at MSU’s Sleep and Learning Lab in the evening before splitting into three groups. The first group went home to sleep normally. The second group stayed overnight at the MSU lab and took either a 30 or 60-minute nap. Finally, the third group stayed but did not nap at all to simulate sleep deprivation.

The following morning, each volunteer repeated the same mental tasks from the day before. These tests measured both attention and a skill called placekeeping — the ability to complete a series of instructions in order without a mistake, even after being interrupted.

“The group that stayed overnight and took short naps still suffered from the effects of sleep deprivation and made significantly more errors on the tasks than their counterparts who went home and obtained a full night of sleep,” Fenn reports. “However, every 10-minute increase in SWS reduced errors after interruptions by about 4%.”

Although those gains are relatively small, the MSU researchers say even a four-percent decrease in mental errors can mean the difference between life or death for sleep-deprived workers, such as doctors, police officers, and truck drivers.

“Individuals who obtained more SWS tended to show reduced errors on both tasks. However, they still showed worse performance than the participants who slept,” Fenn concludes, adding that it appears no kind of nap can replace a full night’s sleep.

The study appears in the journal Sleep.

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