We define naps as mid-day sleeping of under an hour. Longer sleep periods during the day are called siestas.
Recent research actually shows that midday naps can reduce the risk of cardiovascular disease, especially for males. A report published in the Annals of Internal Medicine reported on a large-scale study of people in Greece. Naps reduced the risk of heart problems about as much as statin drugs do.
A study in 2006 concluded that regular naps of less than 30 minutes can improve productivity and mental performance. Regular longer naps are associated with higher mortality. The authors felt that regular nappers could get the most out of their naps by “training” the body to awaken after a short nap.
People who napped at least 30 minutes a day, three times a week, were 37 percent less likely to die from heart disease. Occasional nappers had a 12 percent reduction. Although there is always a risk that daytime naps lead to nighttime insomnia, individuals can learn the specific needs and response of their bodies. Many people can nap in the daytime without nighttime problems. A study of seniors in a retirement community found no significant impact of napping.
Between 2 p.m. and 4 p.m., your body naturally experiences a small dip in temperature, signaling the brain to produce the sleep-inducing hormone melatonin. Sleep plays an important, if not wholly understood, part in formation of long term memory. Memories are consolidated during sleep. Brain researchers have shown events they call “spindles” happen in Stages 1 and 2 and these seem to be connected with memory formation and learning. Short naps can be very effective in facilitating learning. They are especially effective in consolidating learning of new motor tasks. Thus the “power nap”. It is thought that power nap might accelerate memory consolidation by inducing NREM sleep. More here. And here.
One theory is “synaptic pruning” takes place during sleep. This holds that during waking period synapses grow stronger and the number of synapses increases, crowding out the brain’s ability to absorb more information. Sleep is a time when the brain eliminates the number of synapses and frees up resources for further learning. Previous learning is sent to long-term memory. This theory has some animal evidence to support it, but it is just a theory.
You might hear about microsleep periods and think these are naps. They are not. Microsleep is unintentional brief (as little as a few seconds) of sleep, often of only part of the brain, and usually unknown (not consciously perceived) by the person. You do not want to have microsleep episodes. Indeed, intentional naps are a preventative measure against microsleep.
Retired people take a lot of naps because they have less structured days than younger people, but those of all ages can take naps.
How to take a power nap
What used to be called a catnap is now called a power nap. The word “power” makes it acceptable for working adults who think of themselves as on the top of their game and helps sell napping to people who might otherwise think of it as an activity for small children and old people. Calling is a “power nap” makes it socially acceptable.
Usually the power nap is under 20 minutes, so the brain doesn’t have time to go through all the phases of sleep. Longer naps often leave the person groggy upon waking, but power naps can be refreshing without a sleepy hangover.
Some people take their power nap at their place of work – at their desk chair for instance. More ambitious nappers have a cot near their office or even go out to their car for a nap. Most do not use alarm clocks. Trivia: the Prophet Muhammed was a fan of napping and advised people to nap.
The Boston Globe published a one-page guide to napping. It’s pretty good although for some reason they include a drawing of a monkey in the tree.
Naps or Extra Nighttime Sleep
All other things being equal, what is better: an afternoon nap or getting more sleep at night? There is no correct answer of course, but the addition of 30-45 minutes in nighttime sleep does not significantly affect measures of vigilance and daytime sleepiness the next afternoon. Mid-day naps do improve performance on the psychomotor vigilance test and they make people less sleepy in the afternoon as measured by the MSLT. Caffeinated beverages also help us over the mid-afternoon hump more than extra sleep at night, too.
Little kids often nap as part of their regular day. Old people are also stereotypical nappers. In both these cases, age-related sleep patterns can explain part of the predilection. A Pew Reseaech Center survey found that 34% of U.S. adults nap on any given day. Among those past age 80, the percentage was 52%. Men are more like to nap than women and regular exercisers were more likely to nap than sedentary people.
The timing of the nap affects the sleep architecture. Morning naps and afternoon naps differ, with people tending to drift off faster in the afternoon for longer naps with more slow-wave deep sleep than morning naps.
The Science of the Perfect Nap
Daytime Napping – Appetitive and Preparatory
Sleeping is fun, and one of the most fun ways to sleep is daytime napping.
There are many ways of napping. Different lengths, locations, and times of day. Some people have a regular nap in the afternoon (common in toddlers and retired people). Others have a catnap during their lunch breaks. Opportunity and preferences play a big part in napping behavior.
Working adults who nap usually do so in short bursts – the power nap. Weekends present the opportunity for longer naps. Power naps do not last long enough to get to slow-wave sleep. Even short naps can be refreshing.
Toddlers and small children usually need an afternoon nap, and this nap lasts an hour or more. In contrast to adult nappers, toddlers more often go into deep sleep. Kids need lots of deep sleep to support their growth.
Some investigators distinguish between appetitive nappers and replacement nappers.
Appetitive nappers can nap at almost any time, and do so often to “tune out” of their surroundings. Replacement nappers are trying to catch up on sleep. Appetitive nappers can nap even when not sleepy, like an afternoon nap. Replacement nappers are usually not in the mental state or habit that allows them to sleep at will. These are generalizations, of course, and not necessarily fixed.
Another way to classify napping is by saying some naps are prophylactic and some are recuperative, respectively before or after sleep loss. The planned naps before anticipated periods of busy work can raise performance and cut the risk of sleepiness during times when a person needs to be at the top of his or her game.
Naps to Help Us Remember
Research continues to show that daytime napping can improve mental performance in adults, which led to enthusiasm behind the mid-day power nap as well as preparation naps for hurry-up-and-wait occupations such as surgeon and airline pilot. National Geographic even had an article in which they compared the brain to an email system, “sleep—and more specifically, naps—is how you clear out your inbox.” That’s too simplistic, of course, but sleep in general makes us more receptive to learning.
So we know naps can help us remember things we just learned, but are they better than equivalent period of time awake a relaxing or watching television?
Yes, the time spent in napping is better for remembering than the time spent awake.
Longer sleep durations such as nighttime sleep are even better for memory than daytime naps. However, research has established that the gains in improved memory occur in the first half of the night. A sleep period of 3.5 hours is pretty much as effective as a period of 7 hours.
This meshes with the idea that REM (which occurs more in the latter half of the period) is not important in memory formation. This study also confirmed that Stage 2 sleep (particularly early in the night) is important in learning new motor skills.
Naps over 30 minutes usually bring post-nap inertia, though. If the sleeper goes into State 3, slow-wave sleep, it will be harder to wake up. The cognitive benefits of the longer naps last longer, too.
Children are great nappers, partly because they are learning so fast. Many preschools and kindergartens incorporate time for napping in the child’s day. Research has shown naps help children remember things learned earlier in the day and that the children who get the most cognitive benefits are those who nap habitually. When a child skips a regular nap and makes up for the lost sleep time by extending nighttime sleep, the cognitive benefits are not recovered in the makeup sleep.
Hammocks are great for napping, too, and researchers have found that the rocking motion of the hammock facilities falling asleep.
Swinging makes you fall asleep faster and extends the length of the nap, which is why the hammock and similar moving platforms are ideal for appetitive napping. Riding in a car helps some people sleep (one hopes they are passengers, not the driver).
Insomniacs, especially those attempting sleep restriction therapy, are discouraged from daytime napping because it could make it harder to sleep at night.
Napping can be taken as a sign of excessive daytime sleepiness, a symptom of many sleep disorders, but this is an example of how we look at sleep differs whether we are looking for pathologies or recreation. Recreational and appetitive naps are fun, and not a sign of a disorder.
The Caffeine Nap
Sleep researchers at the University of Britain at Loughborough did several tests on fatigued drivers to compare the effects of different methods for a driver can use to stay awake. They put the volunteers in driving simulators while they were sleepy and let them drive. Some of the tests included rolling down windows for cold exposure, blasting the radio and slapping oneself in the face to try to stay awake. But what researchers found worked the best was a Caffeine Nap.
The Caffeine Nap is simple: you drink a cup of coffee and immediately take a 15-20 minute nap. Researchers found coffee helps clear your system of adenosine, a chemical which makes you sleepy. The combination of a cup of coffee with an immediate nap chaser provided the most alertness for the longest period of time in tests. The recommendation was to nap only 15 minutes, no more or less and you must sleep immediately after the coffee.
Most adult Americans drink coffee, and caffeine is possibly the most widely used and longest self-administered drug in mankind. Caffeine is a stimulant and is often used when people want to stay awake. The caffeine nap is an example of the paradoxical effect of many substances in the body.
A Stanford University test published in 2010 found that caffeine during the day disrupts night sleep more in morning people (larks) than in evening people (owls).
Sleeping better on stimulants
The tradition of the siesta in some countries and cultures has posed a question for a long time: is taking a siesta on a regular basis good for you?
Determining this type of thing is tough. It has long been known that people in these countries generally have lower rates of fatal heart disease than in siesta-less countries, but nobody ever knew if there was a cause and effect relationship. Maybe other factors such as diet were responsible for fewer heart attacks. A study conducted by epidemiologists at the University of Athens in 2007 attempted to find out. Using data from over 23,000 people and sophisticated statistical techniques, they found that siestas were correlated with lower rates in fatal heart attacks, especially in working men.
Meanwhile, a study conducted at Hadassah University Hospital in Israel in 2005 looked at a sample of 455 70-year olds and found that those who practiced siestas had a higher death rate.
An earlier (2003) Israeli study found that long siestas (over 2 hours) were correlated with increased mortality among men, but that shorter naps and siestas for women had no major correlation with mortality. And siestas appeared to be worse among men with chronic health problems.
A 2000 study by Harvard Medical School researchers of people in Costa Rica found that daily siestas in fact increased the effect of heart attacks.
So the evidence is conflicting. Researchers tend to agree that resting in the afternoon without sleeping does not pose any health risk and is often very beneficial.
According to The Economist, the Spanish government recently launched a campaign to eliminate the tradition of siestas. Spaniards reportedly sleep an average of 40 minutes less per night than other Europeans and have the highest rate of workplace accidents in the European Union.