NIOSH Training for Nurses on Shift Work and Long Work Hours

Sleep Inertia

After awakening from a nap or a long sleep episode (for example, 7 to 8 hours of sleep at night), people tend to feel groggy from sleep inertia.

• Sleep inertia is a temporary disorientation and decline in performance and/or mood after awakening from sleep. People can show slower reaction time, poorer short-term memory, and slower speed of thinking, reasoning, remembering, and learning.
• Research indicates this typically can last from 30 to 60 minutes, but researchers have observed it lasting 2 hours^15-17
• Sleep inertia usually does not last longer than 30 minutes, but it can be longer if the person is sleep deprived, according to Tassi and Muzet.¹⁸

• Longer periods of sleep inertia were seen in night shift workers after they took an hour long nap during the early morning hours (about 4 a.m. to 5 a.m.).¹⁹ This was likely due to the strong drive for sleep during this time and the long nap allowing the brain to progress into deeper stages of sleep.
• Newman and colleagues found taking 100 mg. of caffeine on awakening reduced the time of sleep inertia, restoring reaction time more quickly compared to placebo.²⁰ Another strategy is to take caffeine just before taking a short nap.²¹ Caffeine takes about 30 minutes to reach full effect so on awakening the person can experience alerting benefits from both caffeine and the nap and less sleep inertia.
• Bright light and washing the face have also helped restore alertness more quickly after a nap.²²