Sleeping for a short period (i.e. napping) may help mitigate impairments in cognitive processing caused by sleep deprivation, but there is limited research on effects of brief naps in particular. In a new study, researchers from the University of Pittsburgh and Michigan State University tested the effect of brief naps (30- or 60-min) during a period of sleep deprivation.
A brief nap during the day won’t restore a sleepless night. Image credit: Sweet Briar College.
Slow-wave sleep is the deepest and most restorative stage of sleep.
It is marked by high amplitude, low frequency brain waves and is the sleep stage when our body is most relaxed; muscles are at ease, and heart rate and respiration are at their slowest.
“Slow-wave sleep is the most important stage of sleep,” said Dr. Kimberly Fenn, director of the Sleep and Learning Lab at Michigan State University.
“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 slow-wave sleep. When individuals go to sleep each night, they will soon enter into slow-wave sleep and spend a substantial amount of time in this stage.”
For the study, Dr. Fenn and colleagues recruited 275 college-aged participants.
The volunteers completed cognitive tasks when arriving at the lab in the evening and were then randomly assigned to three groups.
The first was sent home to sleep; the second stayed at the lab overnight and had the opportunity to take either a 30 or a 60 minute nap; and the third did not nap at all in the deprivation condition.
The next morning, the participants reconvened in the lab to repeat the cognitive tasks, which measured attention and placekeeping, or the ability to complete a series of steps in a specific order without skipping or repeating them — 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,” Dr. Fenn said.
“However, every 10-min increase in slow-wave sleep reduced errors after interruptions by about 4%.”
“These numbers may seem small but when considering the types of errors that are likely to occur in sleep-deprived operators — like those of surgeons, police officers or truck drivers — a 4% decrease in errors could potentially save lives.”
“Individuals who obtained more slow-wave sleep tended to show reduced errors on both tasks. However, they still showed worse performance than the participants who slept.”
“We hope that the findings underscore the importance of prioritizing sleep and that naps — even if they include slow-wave sleep — cannot replace a full night of sleep.”
The findings were published in June 2021 in the journal Sleep.
Michelle E. Stepan et al. Slow-wave sleep during a brief nap is related to reduced cognitive deficits during sleep deprivation. Sleep, published online June 22, 2021; doi: 10.1093/sleep/zsab152