The Science of Napping
Simple guidelines to nap like a champ
By Dr. Dan Gartenberg
Last Updated: March 30, 2023
How long should my nap be? What is the perfect nap time of day? How do I get a deep nap that doesn’t leave me feeling groggy? Can naps make up for a lack of sleep?
These are common questions that have a scientific answer. There are different types of naps that are optimal based on your sleep needs, anticipated sleep needs, and the time of day.
Napping is one of the best (and easiest!) things that you can do for your health, work performance, and general well-being. Scientific evidence has shown that napping can improve waking performance and alertness, even after a normal night of sleep. It is the best way to counteract that grogginess that occurs when you’re sleep deprived or feel tired at 4 pm when your circadian alertness decreases.
Napping can be immensely helpful to your work life and your day, but napping the wrong way can leave you feeling drowsy and grumpy. Keeping the following guidelines in mind can help you avoid these negative side effects:
1) Never nap if you have problems falling asleep and staying asleep
Napping can be a great way to optimize consciousness and performance. However, if you have problems falling asleep and staying asleep, there is consensus in sleep science that you should never nap. The reason for this is that napping will reduce the buildup of adenosine, which is a neurotransmitter that increases throughout the day in order to make the brain tired. In other words, if you nap, you will be less likely to be tired when you ought to go to bed. This can make problems falling asleep and staying asleep much worse. As shown in the graph below, taking a nap can flatten your circadian rhythm, which can be counterproductive to health and well-being. Disclaimer: If you drive for a living, operate heavy machinery, or have a job that could cause serious accidents you can ignore this device and make sure you are fully rested in any way possible to complete your job.
2) The ideal time for a short nap is under 30 minutes or over 90 minutes
In general, it’s best to avoid waking up during the deep sleep phase. The danger zone of napping is between 30 to 80 minutes. If you wake up during this window, it’s likely that you’re waking up during the deep sleep cycle. This will leave you feeling groggy and confused when you awaken, keeping you from feeling refreshed.
3) Try to nap in early afternoon during your circadian dip
It’s also best to nap when the circadian component of sleep is low so that it doesn’t take long to fall asleep. Late afternoon naps can keep you from falling asleep that night.
4) Different types of naps are appropriate for different circumstances
Replacement Naps are best for when you are sleep deprived, Appetitive Naps and Micro-naps help to improve performance, and Prophylactic Naps are used in preparation for sleep deprivation
Replacement Naps / A Full Sleep Cycle Nap
Replacement Naps are taken to make up for previous sleep loss. These naps should be long to ensure the restorative powers of a complete sleep cycle. For example, if you are sleep deprived and you feel tired, a longer nap of about 90 minutes may be appropriate. A 90 minute nap means that you will likely go through an entire sleep cycle. Sleeping for an entire sleep cycle will help you feel refreshed and more alert, while also ensuring that you do not awaken in deep sleep.
If you are not sleep deprived, then shorter naps of less than 30 minutes are best. These are called 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 can improve your performance. These types of naps that are taken in advance of sustained wakefulness are known as Prophylactic Naps. The key to these naps is to sleep before the period of sleep deprivation. Taking prophylactic naps can help keep you alert and focused.
A micro-nap is a very short nap that lasts between 1 and 6 minutes. It is a great way to quickly recharge your batteries and boost your energy levels. Micro-nap are best for those who want to quickly regain their focus and energy levels without feeling sleepy or tired. These naps are helpful for a cognitive boost if you are already getting a healthy amount of sleep.
A caffeine-nap, also known as a coffee nap, is a strategy for combating fatigue that involves consuming a caffeinated beverage, such as coffee or tea, and then immediately taking a short nap. The idea behind the caffeine-nap is that the caffeine takes approximately 20-30 minutes to take effect, so by napping during that time, you can wake up feeling more alert and refreshed. The caffeine enhances the effect of the nap, helping you feel more awake and energized when you wake up. The ideal length for a caffeine-nap is around 20-30 minutes, as longer naps may result in sleep inertia or grogginess upon waking up.
Avoid long naps
While naps can be a great thing for healthy sleepers, if you have problems falling asleep and staying asleep, then most sleep experts agree that long naps can make your sleep rhythms worse and make it harder to go to sleep that night. This is because we all have a certain amount of sleep we need each day. This is called a sleep allowance or a sleep bank. When you nap for longer than about half an hour, you are taking sleep time out of your nighttime sleep need.
As you can see in the above graph: the top chart represents healthy sleep, without a nap, and the bottom graph represents what happens to our rhythms when we take a nap. As can be seen by the change in your sleep drive (the arrows pointing down), taking a nap reduces your sleep drive, which then makes you more alert during the night time when you should be tired.
Taking a nap, especially a long one, will make it harder to fall asleep at your bedtime and/or stay asleep. It can also shift your circadian rhythm later, making it hard to fall asleep and wake up for several days in a row. Therefore, it is important to avoid long naps, if at all possible. This rule will help your body to acquire a consistent sleep rhythm so that you feel drowsy and ready to sleep at about the same time each night.
People frequently take naps because they think they need to catch up on the sleep they missed or simply because they are tired and think they need a nap to get through the day. If you often feel the need to nap in the early afternoon, this is a normal part of the circadian rhythm called the “post-lunch dip.” It’s OK to take a short nap during this time, and this is a popular practice in many cultures. But problems falling asleep later on in the day can occur when your naps last for over 30 minutes. Make sure to set a smart alarm by changing the wake up time in the SleepSpace app to help you wake up from a nap, in order to ensure you keep it brief. Another option is to try to get active and get some light exposure during times you think you need to nap. The best way to do this is going for a walk outside, if at all possible. This will increase alertness and help you sleep better at night. If you can’t go outside, another option is purchase a happy lamp that emits light at 10,000 lux. Dr. Gartenberg recommends the Verilux lamp. Finally, brainwaves can be regenerative even if you don't fully fall asleep, but instead do a relaxation, such as Yoga Nidra, found within the SleepSpace app.
Neuroscience and sleep is one of the final frontiers of human exploration.
What are the different phases of sleep?
REM sleep vs Non-REM Sleep. REM sleep is “almost magical” for your brain.
In the US there are 4 stages of sleep.. but in Europe there are 5 stages of sleep… this demonstrates that our understanding of sleep is still VERY early stage.
“N1 Sleep” - the transition between the conscious and unconscious mind.
You want more REM and you want more DEEP SLEEP and not more light sleep.
Deep sleep is how you prune, REM is how you integrate.
When you are in deep sleep your brain is operating on delta waves.. which are a completely different experience to waking life.
Learn more about the science of napping in the Science of Success podcast
Some additional topics discussed include:
When should you nap? Is napping good for you?
Taking a power nap right at your circadian dip is often an optimal performance strategy.
What is your circadian rhythm and how can it shape your sleep schedule and performance?
What is “chronobiology” and how it can help us be more productive and effective?
The importance of sunlight in controlling your circadian rhythm.
How does intermittent fasting interact with your daily energy levels and circadian rhythms?
What are the hacks and strategies for improving your sleep quality and getting more out of your deep sleep?
Tip: get rid of noise pollution when you’re sleeping.
Scientific Research on the Benefits of Naps
Naps can reduce the risk of heart disease: A study of over 23,000 Greek adults found that those who took regular naps had a 37% lower risk of dying from heart disease.
Naps can improve physical performance: A study of professional athletes found that a 20-minute nap improved their sprint performance by 3.3%.
Naps can improve immune function: Studies have shown that napping can improve our immune function and reduce the risk of illness. One study found that napping for 2 hours or more improved immune function by up to 40%.
Naps can improve cognitive function: Studies have shown that naps can improve our cognitive function, including memory, attention, and creativity. One study found that a 60-minute nap improved participants' memory retention by 5 times compared to those who did not nap.
Naps can improve mood: Napping has been shown to improve mood and reduce stress levels. Studies have found that napping can reduce levels of cortisol, a hormone associated with stress.
Can naps make up for sleep deprivation?
• Naps cannot make up for chronic sleep deprivation: Chronic sleep deprivation, which is a consistent lack of sufficient sleep over a period of time, cannot be fully compensated for by napping. While napping can help alleviate some of the effects of sleep deprivation, such as fatigue and decreased cognitive function, it cannot fully replace the benefits of a full night's sleep.
• Napping cannot provide all stages of sleep: A full night's sleep consists of several stages of sleep, including deep sleep and REM sleep. Napping typically only provides the lighter stages of sleep, such as stage 1 and 2, which are not as restorative as the deeper stages of sleep.
• Naps can disrupt nighttime sleep: Napping too close to bedtime or napping for too long can disrupt nighttime sleep, leading to further sleep deprivation. Napping should be done earlier in the day and for a shorter duration to avoid interfering with nighttime sleep.
• Naps do not address the root cause of sleep deprivation: Sleep deprivation can be caused by a variety of factors, including poor sleep hygiene, underlying health conditions, and lifestyle habits. While napping can help alleviate some of the effects of sleep deprivation, it does not address the root cause of the problem.
• Napping cannot provide the same benefits as a full night's sleep: While napping can provide some benefits, such as increased alertness and improved cognitive function, it cannot provide the same benefits as a full night's sleep. A full night's sleep has been linked to numerous health benefits, including improved immune function, better memory consolidation, and a reduced risk of chronic health conditions.
All this being said, one reasonable strategy that would still be considered healthy sleep is to sleep for 20 minutes less than you need at night and then take a 20 minute nap during your afternoon dip. Since the last 20-minutes of sleep are light sleep anyways, when you are getting enough sleep, this will provide you with all the stages of sleep throughout the night and the charge of a nap in the afternoon. This could be considered the best of both world, and the most effective way to use naps.