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