Scientific evidence has shown that napping can improve waking performance and alertness, even after a normal night of sleep. Additionally, it counteracts the decreased alertness experienced when sleep deprived .
There are general guidelines for napping that when followed, can optimize the effectiveness of a nap. For example, you should nap when the circadian component of sleep is low in order to reduce how long it takes you to fall asleep. Also, taking a nap that is longer than 30 minutes but less than 80 minutes increases the likelihood of awakening during deeper sleep, which can be counterproductive to your alertness and energy level . Lastly, napping longer than 30 minutes or in the late afternoon can interfere with the following night of sleep .
Furthermore, different types of naps are appropriate for different circumstances. This includes taking 1) Replacement Naps when you are sleep deprived, 2) Appetitive Naps to improve performance, and 3) Prophylactic Naps in preparation of sleep deprivation.
Replacement Naps are taken to make up for previous sleep loss. These naps should be longer to ensure the restorative powers of a complete sleep cycle. For example, if you are sleep deprived and homeostatic pressure to fall asleep is high, a longer nap of about 90 minutes may be appropriate. Sleeping for an entire sleep cycle confers the greater restorative benifits of sleep while also ensuring that you do not awaken in deep sleep.
On the other hand, if you are not sleep deprived shorter naps of less than about 30 minutes are advised. These are labeled Appetitive Naps. In a recent study, people who took less than 20-minute naps in the mid-afternoon experienced increased work performance and rated themselves as being less tired .
The best time to take a nap can also be influenced by how long you plan to be awake. If you know that you are going to stay awake for a long period of time, taking a nap prior to this period of sleep deprivation benefits performance. These types of naps that are taken in advance of sustained wakefulness are known as Prophylactic Naps. Thus, it may be better to nap prior to sleep deprivation than during the period of sleep deprivation.
A future goal of Proactive Sleep is to be able to predict which type of nap you should take so you feel more refreshed.
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