Institute for Continuing Education

Sleep Inertia, Naps, and Memory

Course Objectives

Upon successful completion of this module, you will be able to:

• Define and discuss what is meant by “sleep inertia”.
• Explain its symptoms, epidemiology, frequency of occurrence.
• List the potential treatments and preventive actions that can be taken regarding sleep inertia.

Course Information

The media has recently been full or stories regarding something commonly referred to as Sleep Inertia, and this CEU offers you a brief review of what is being said, and some facts about the phenomenon.

While a sleep-deprived medical resident’s cognitive impairment may be similar to that of an uncoordinated drunk, the impairment of a resident who is shaken awake from a nap may be even worse, researchers said.

But the cognitive effects of so-called sleep inertia-the state of grogginess and disorientation commonly experienced on waking-only last for minutes, said Kenneth P. Wright Jr. Ph.D., of the Sleep and Chronobiology Lab at the University of Colorado.

Still, sleep inertia may sometimes affect the performance of doctors, emergency medical technicians, and firefighters, Dr. Wright and colleagues reported in a research letter published in the Jan. 11 issue of the Journal of the American Medical Association.

The study involved eight men and one woman, all paid volunteers from 20 to 41 years old. They were free of medications, alcohol, nicotine, recreational drugs, and caffeine for three weeks before the study, verified by toxologic analysis. The volunteers’ professions were not disclosed.

For six nights, the volunteers got a good night’s sleep (about eight hours) in the lab. On the morning after the sixth night, they were awakened and immediately given a cognitive performance test involving adding randomly generated, two-digit numbers.

Volunteers were given the test at 20-minute intervals in the morning and hourly intervals for the rest of the day and night. They were deprived of sleep for the next 26 hours, being tested all the while, so the researches could compare the effects of sleep deprivation to those of sleep inertia the volunteers experienced in the morning.

On average over the 26-hour study period, the volunteers scored 23 correct answers on a 28-question test. Immediately after waking, however, the average score was at a rock-bottom of 17. Twenty minutes later, the score rose to 23.

The score climbed to 25 four hours later and leveled off during the day, with a dip in the afternoon, and sank again after one night of sleep deprivation to 21-still much better than the average score immediately upon waking, the researchers noted.

“This is the first time anyone has quantified the effects of sleep inertia,” Dr. Wright said. “For a short period, at least, the effects of sleep inertia may be as bad as or worse than being legally drunk.”

The study has implications for medical professionals who are often called on to tend patients in crisis on a moment’s notice, often at odd hours, Dr. Wright said. Medical residents, for example, who may work 80 hours or more per week and who catnap at times, could be prone to make simple math mistakes when calculating dosages of medicine during bouts of sleep inertia, he said.

“The present results may have important implications for occupations in which sleep-deprived personnel are expected to perform immediately on awakening from deep sleep, including physicians, truck drivers and pilots arising from on-board sleeper berths, and public safety and military personnel,” the study authors concluded.