Naps

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Naps

A nap is simply just going to sleep during the middle of the day. The definition is simple. It makes sense. You are tired during the day, and so you take a nap.  You didn’t get enough sleep at night, so you take a nap. Or, perhaps, naps are built into your daily routine.

As children, we grew up napping. Infants can take over 4 naps per day. Children take naps. I remember naps being a part of school. As a adults, we tend to take naps to alleviate the effects of not getting enough sleep or to ensure productivity across the day.

There has been a lot of scientific research on the benefits of napping, their potential negative effects, and how to take the ideal nap. 

In my opinion, a lot of this research doesn’t make sense. For example, a 10-20 minute nap is frequently stated as the ideal length, but the same research shows it takes people 10 minutes to actually fall asleep during a nap. 

In addition, so much of the research is focused on what would make us more productive. So many of the recommendations on napping are biased to ensure we have time to be productive. It is not biased to ensure we thrive optimally.

Sleep stages, circadian rhythm, and homeostatic drive

Three aspects of sleep science are needed to be discussed to fully understand naps. 

Sleep Stages

First, sleep isn’t just turning off or resting. Rather the brain and body are doing very specific things. Sleep is composed of four distinct states:

Stage 1: This is a transitional state from wake that will last 1-5 minutes.

Stage 2: This is generally described as light sleep. This will last 10-60 minutes. Please note that even though this stage is thought of as light sleep, it is just as important as the other stages of sleep.

Stage 3/4 or Slow Wave Sleep: This is generally though of as deep sleep. It is also called slow wave sleep, called this because the activity of the brain begins to be synchronized and produces slow waves of activity when you monitor brain activity. This will last for 20-40 minutes.

REM Sleep: REM stands for rapid eye movement. It is generally thought of as dream sleep because this is the stage of sleep in which we have our most vivid and complex dreams. This stage will last for 10-60 minutes.

We will cycle through each stage of sleep, starting at stage 1, going through stage 2, then slow wave sleep, then REM sleep, and then repeats a number of times throughout a night of sleep. 

The amount of time we spend in each stage changes through out the night. At the beginning of the night, we will have short stage 2 and REM sleep periods, but more slow wave sleep. But, later in the night we will have longer stage 2 and REM sleep periods, with less slow wave sleep.

Circadian Rhythm

Second, we have circadian rhythm. This is our internal clock that tracks what time it is. The circadian rhythm is a name for all of the processes that regulate sleep and wake. We tend to fall asleep at the same time each day. We tend to wake up at the same time each day. We also tend to feel sleepy at the same time each day in the afternoon.

Homeostatic Drive

Third, there is the homeostatic drive. Homeostasis simply means “same state”. We have a homeostatic drive for sleep, meaning our bodies want a certain amount of sleep and will seek to maintain that level of sleep.

This is the same sort of drive as hunger or thirst. We need to consume a certain amount of food per day. If we do not, we will feel hungry. If we skip a meal, then we might eat more food during our next meal. 

Our drive for sleep behaves in a very similar way. If we sleep poorly one night, we will feel tired the next day and our bodies will want to sleep for a longer period than normal. 

However, we have a homeostatic drive for each stage of sleep. Our bodies and brains want a certain amount of slow wave sleep and a certain amount of REM sleep. 

For example, if I fall asleep at my normal time, but wake up 2-3 hours earlier than normal, then I will be missing REM sleep. This is because slow wave sleep happens early in the night and most of my REM sleep occurs at the end of the night. The next time I fall asleep, REM sleep will occur earlier in the night.

Why we nap and the reasons for napping

With that in mind, you might want to conclude that we nap simply because we didn’t get enough sleep or that we simply feel tired in the afternoon because of our circadian rhythm. But things aren’t so simple.

Scientists have done research on why people nap and have suggested a number of reasons for napping.

  • Dysegulative naps. People take naps in order to compensate for trouble sleeping because of a work schedule that prevents sleeping at night, illness, pain, or exercise.
  • Restorative naps. People take naps because of a poor night sleeping or to prepare for a poor night of sleep.
  • Emotional naps. People take naps because they want to improve their mood because of stress, depression, or boredom. Or they might want to avoid work or a social situation.
  • Appetitive naps. People take naps because they enjoy them and have made them part of their lives.
  • Mindful naps. People take naps in order to refocus, increase alertness, attention, and energy. People take naps because they believe naps will help them achieve this.

Another set of scientists have categories naps into slightly different categories:

  • Recovery naps: Naps taken because of sleep loss. 
  • Prophylactic naps: Naps taken before sleep loss. 
  • Appetitive: Naps taken because naps are enjoyable.
  • Fulfillment: Naps taken due to increased sleep need. For example, children need to take naps for this reason.
  • Essential: Naps taken because of sickness.

Are naps good or bad?

Researchers have recently reviewed the science on the benefits and the risks of napping. They find both positive and negative aspects of napping. 

Benefits of a nap

They note the following positive benefits of napping:

  • Naps benefit cognitive functions like attention and working memory
  • Naps reduce homeostatic sleep pressure
  • Naps promote memory consolidation
  • Naps prepare your brain for learning
  • Naps promote emotional processing

Potential negative effects of napping

They also note the following negative effects of napping

  • Naps containing slow wave sleep increase the feeling of sleepiness immediately after napping
  • Frequent napping has been associated with a number of negative health issues like “increased risk for hypertension, microvascular sears, depression, diabetes, osteoporosis, functional limitations, general medical morbidity, increased mortality, and cognitive decline”. The authors note that these have been primarily identified in older faults, but these increased risks have also been observed in people across the lifespan.

However, it should be noted that increased risk for negative health outcomes are simply associative. There simply isn’t good evidence to say that naps have caused these outcomes. Correlation is not causation. Indeed the authors of the study state, “ it is possible that naps themselves are not detrimental but instead are a byproduct or side-effect of pre-existing health issues or typical age-related brain and body degradation. Based on the literature discussed, we believe this to be the most plausible explanation.”

What is a power nap?

There is a lot of different articles and media suggesting power naps, which are naps of less than 10-30 minutes:

There is some science to back up these claims:

Length of power nap 

In addition, this makes sense from an understanding of sleep stages. We go through our sleep stages sequentially. Naps of less than 20 minutes will ensure that slow wave, or deep sleep, is not reached. This is important because if you reach slow wave sleep, it will be harder to wake up and you will wake up with a feeling of sleepiness or grogginess. 

Generally, we take naps to reduce this feeling of sleepiness and to increase a sense of alertness. It is counter productive to take a nap and wake up feeling even more tired and sleepy.

Finally, naps of this short duration are unlikely to interfere with falling asleep at night. The homeostatic drive for sleep is an important factor in being able to fall asleep at night. The less sleep you get, the more your body and brain will want to sleep, and the easier it will be to fall asleep. Taking a long nap can reduce this pressure for sleep, making it more difficult to fall asleep at night.

Are 10-20 minute naps are ideal?

In research for this article, I came across this recommendation for 10-20 minute naps so frequently that I began to be worried about it. Why is everyone recommending 10-20 minute naps? Does this even make sense? Is there actually science to base this upon?

After my review, I do think that there is sufficient evidence to say that 10-20 minute naps are beneficial. I do not think that this would be considered the ideal length of time for a nap.

There are reasons for my skepticism. 

First, it takes people 10-15 minutes to fall asleep. A study on napping reports that it took people, on average, about 12 minutes to fall asleep. This means that if you take a 10 minute nap, you will likely not even sleep. From a common sense point of view, this does not make sense. 

Second, sleep science is relatively new and began with a bias against napping. In addition, we have cultural biases against napping, thinking that naps are for lazy people or children. 

Third, so much of the research on naps is focused exclusively on productivity. For example, the frequently referenced recommendation of 26 minutes by NASA was based to identify nap duration for fighter pilots. Many of the tasks used to assess cognitive function after napping are basic attention. 

The recommendation for 10-20 minute naps are biased toward productivity

This is very clearly stated in a review of the scientific literature on naps:

In general, based on the research outlined above, healthy young adults should ideally nap for approximately 10 to 20 min]. These short naps are ideal for workplace settings where performance immediately upon awakening is normally required. 

I believe this to be the reason why 10-20 minute naps are so frequently recommended. They provide a benefit of increased attention and reduced sleepiness, without the time commitment of longer naps. They allow us to take a quick break and quickly return to being productive. 

This is wonderful in a society that requires so much productivity, but this may not mean that 10-20 minute naps our ideal for our individual health and well-being. It just means that a 10-20 minute nap is a good tradeoff between the benefits and costs of napping.

Cultural views towards napping and sleep

It is nearly obvious that the invention of electric lights have changed how we sleep. A lot of us live in cultures that value consolidated sleep starting in the middle of the night. We spend out days at school or work, with no break for naps. We return home and stay awake until a few hours after sunset. 

But there are other ways people have slept. There are biphasic sleep schedules that may include a moderately long period of sleeping at night and a shorter nap during the day. or breaking the night into two segments of sleep.

There has been recent discussion around first sleep and second sleep, a biphasic pattern of sleep in which people would sleep for 4 or 5 hours, wake up for 1 or 2 hours, and then return to sleep for 4 or 5 hours. It is, however, very difficult to research how people slept in the past.

There are also cultures that still engage in biphastic sleep. For example there is the siesta culture of taking a midday nap.

Sleep maintenance insomnia

Sleep maintenance insomnia is a type of insomnia in which people are able to fall asleep, but they wake up in the middle of the night, unable to return to sleep. Interesting, the advice to treat sleep maintenance insomnia is generally to avoid napping, especially in older adults.

However, Professor Matthe Wolf-Meyer has speculated that sleep maintenance insomnia could be ameliorated by adapting our cultural expectations of sleep to that of the individual by allowing people to nap in the day. Perhaps this type or subtypes of insomnia is simply evidence that humans sleep in a variety of ways and it is harmful to expect every person to mold themselves to one standard of sleep.

What is the best length for a nap?

Because of all this research, we think the ideal length of a nap is whatever feels good to you. If you can and want to take a 10 minute nap, then that is wonderful. If you can and want to take a 90 minute nap, then that is also wonderful.

The ideal length of nap is what feels good to you

Naps of 10-30 minutes have been shown to improve alertness and reduces feelings of sleepiness. In addition, you will likely not reach slow wave sleep, so you will wake up without a feeling of grogginess or sleepiness. This duration of nap is unlikely to impact your homeostatic drive, so you will likely not encounter any difficulties falling asleep at night.

You will likely progress to slow wave sleep if you nap for more than 30 minutes. If you have to wake up during this stage of sleep, you will likely feel sleepy and groggy. Slow wave sleep also will impact your homeostatic drive for sleep. This is good if you’re trying to overcome a previous night of poor sleep or are preparing for an upcoming night without sleep. But, this can also impact your ability to sleep at night.

We tend to progress through all of the stages of sleep every 90-120 minutes. As a result, this can also be a good duration of nap since you would likely wake up during REM or stage 2 sleep, which can result in less feelings of sleepiness than if you woke up during slow wave sleep.

What is good sleep?

Naps can impact how we sleep at night. Regardless of what duration of nap you choose, be aware of how it can impact your ability to fall asleep at night. If you take a 90 minute nap, then just pay attention to how you sleep that night.

What is the best time for a nap?

The best nap timing is the time that works best for you. If you’re able to find a time in which you can fall asleep, wake up rested, and not disturb you nightly sleep, then you’ve found the best time for a nap.

However, it is generally suggested that taking a nap right after lunch time in the early afternoon is an ideal time to take a nap. This is because of our circadian rhythms. We naturally have a point in the early afternoon where we feel tired and napping is easier.

Additionally, taking a nap later in the afternoon or in the evening has the possibility of disrupting sleep later that night. This is because of the homeostatic drive. Napping can reduce the pressure to sleep. You simply feel less sleepy after naps. However, you generally need to have sleep pressure or a sense of sleepiness to fall asleep at night.

Do we dream during naps?

This review would not be complete without talking about dreams. Naps can reveal a lot about how we dream.

On the one hand, we know that REM sleep generally only occurs after stage 1, stage 2, and slow wave sleep. In addition, the first REM sleep period is generally quite short compared to later in the sleep. Therefore, we might expect that we do not dream during shorter naps.

On the other hand, I have had very intense and vivid dreams during naps. I know that I dream during naps because I have had dreams during naps.

Interestingly, dream recall seems to be improved during naps. In this study, researchers observed people napping and woke them up to ask them to report any dreams. 

They found that people reported dreams 96% of the time when woken up from REM sleep and 89% of the time when woken up from non-REM sleep. By comparison when dreams are recalled about 80% of the time when people wake from REM sleep and 43% of the time when people wake from non-REM sleep.

So we do dream during naps, even if we do not sleep for a full sleep cycle and reach REM sleep.

Conclusion

Naps can be an important part of sleeping well. Most scientists and researchers suggest taking naps of less than 30 minutes, but these are easier to fit into the day and you won’t wake up sleepy or groggy. 10-20 minute naps are unlikely to interfere with sleeping at night.

However, this could be only one view on napping. Some people routinely build naps into the fabric of the day. Some people take naps for longer. The ideal nap length is the nap length that works best for you.

DreamWell is aimed at helping you sleep, dream, and be well. As a result, we encourage naps if they help you sleep well. We offer specific practices for naps if you want to work with your dreams while you nap or approach napping as part of a mindful practice. Alternatively, listening to sleep sounds or music during a nap could be beneficial. But we are happy as well if you simply want to explore naps on your own.

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