Welcome to the I Can't Sleep Podcast,
A space to quiet your mind and ease into rest.
I'm Benjamin Boster,
And tonight I'll be reading about naps in a calm,
Soothing voice.
Take a deep breath,
Settle in,
And let's begin.
A nap is a short period of sleep,
Typically taken during daytime hours,
As an adjunct to the usual nocturnal sleep period.
Naps are most often taken as a response to drowsiness during waking hours.
A nap is a form of biphasic or polyphasic sleep,
Where the latter terms also include larger periods of sleep in addition to one period.
For years,
Scientists have been investigating the benefits of napping,
Including the 30-minute nap as well as sleep durations of 1-2 hours.
Performance across a wide range of cognitive processes has been tested.
Sarah Mednick conducted a study experimenting on the effects of napping,
Caffeine,
And a placebo.
Her results showed that a 60-90 minute nap is more effective than caffeine in memory and cognition.
A power nap,
Also known as a stage 2 nap,
Is a short slumber of 20 minutes or less,
Which terminates before the occurrence of deep slow-wave sleep,
Intended to quickly revitalize the napper.
The power nap is meant to maximize the benefits of sleep versus time.
It is used to supplement normal sleep,
Especially when a sleeper has accumulated a sleep deficit.
The greater the sleep deficit,
The more effective the nap.
It has been shown that excessive daytime sleepiness,
EDS,
Can be improved by prescribed napping and narcolepsy.
Apart from narcolepsy,
It has not been demonstrated that naps are beneficial.
For EDS and other sleep disorders.
Research suggests that shorter,
Habitual naps after instruction offer the most benefits to learning.
The benefits to alertness show no change based on duration of the nap for combating post lunch dip,
Even for naps as short as 10 minutes.
Napping enhances alertness in young adults and adolescents during afternoon's performances,
Which affect efficiency.
Additionally,
Pre-teens who nap regularly during the day demonstrate better sleep at night.
In younger children,
Napping increased drowsiness,
Even while improving memory recall.
For students of all ages,
Napping during the school days showed benefits to reaction time and recall of declarative memory of new information,
Especially if the naps remain in slow-wave sleep,
I.
E.
Less than an hour in length.
In adults,
A causal association has been found between habitual daytime napping and larger brain volume.
Brain volume normally declines with age and is associated with neurodegenerative disease.
Earlier studies have shown benefits of napping for cognitive performance for healthy adults.
The circadian cycle plays a role in the rise demand for daytime naps.
Sleepiness rises towards the mid-afternoon,
Hence the best timing for naps is early afternoon.
20-30 minute naps are recommended for adults,
While young children and elderly people may need longer naps.
Research,
On the other hand,
Has shown that the benefits of napping depend on sleep onset and sleep phases,
Rather than time and duration.
The state of grogginess,
Impaired cognition,
And disorientation experienced when awaking from sleep is known as sleep inertia.
This state reduces the speed of cognitive tasks but has no effects on the accuracy of task performance.
The effects of sleep inertia rarely last longer than 30 minutes in the absence of prior sleep deprivation.
A 2016 meta-analysis showed that there may be a correlation between habitual napping for more than an hour and having an increased risk for cardiovascular disease,
Diabetes,
Metabolic syndrome,
Or death.
There was no effect of napping for as long as 40 minutes per day,
But a sharp increase in risk of disease occurred at longer nap times.
No causal relationship was established.
The link may be to do with people taking a longer nap in response to the pre-existence of other risk factors.
Habitual naps are also an indicator of neurological degradation,
Such as dementia in the elderly,
As reduction in brain function causes more sleepiness.
For idiopathic hypersomnia,
Patients typically experience sleep inertia and are unrefreshed after napping.
Here are some best practices.
How long and when a person naps affects sleep inertia and sleep latency.
A person is more likely to benefit in terms of those two points when they sleep moderately in the afternoon.
According to research,
The degree to which a person experiences sleep inertia differs in different durations of nap.
Because sleep inertia is possibly resulting from awakening from slow wave sleep,
It is more likely to happen when one has a longer nap.
Sleep inertia is less intense after short naps.
Sleep latency is shorter when a nap is taken between 3 and 5 p.
M.
,
Compared with a nap taken between 7 and 9 p.
M.
According to the Sleep Foundation,
Psychology Today,
And Harvard Health Publishing,
These are the best practices for napping.
Setting up a sleep-friendly environment.
Understanding physical needs.
Setting an alarm in order to prevent the negative impact of sleep inertia and sleep latency.
Polyphasic sleep is the practice of sleeping during multiple periods over the course of 24 hours,
In contrast to monophasic sleep,
Which is one period of sleep within 24 hours.
Biphasic or diphasic,
Bifurcated,
Or bimodal sleep refers to two periods,
While polyphasic usually means more than two.
Segmented sleep and divided sleep may refer to polyphasic or biphasic sleep,
But may also refer to interrupted sleep,
Where the sleep has one or several shorter periods of wakefulness,
As was the norm for night sleep in pre-industrial societies.
A common form of biphasic or polyphasic sleep includes a nap,
Which is a short period of sleep typically taken between the hours of 9 a.
M.
And 9 p.
M.
,
As an adjunct to the usual nocturnal sleep period.
Napping behavior during daytime hours is the simplest form of polyphasic sleep,
Especially when the naps are taken on a daily basis.
The term polyphasic sleep was first used in the early 20th century by psychologist J.
S.
Szymanski,
Who observed daily fluctuations in activity patterns.
It does not imply any particular sleep schedule.
A circadian rhythm disorder known as irregular sleep-wake syndrome is an example of polyphasic sleep in humans.
Polyphasic sleep is common in many animals and is believed to be the ancestral sleep state for mammals,
Although simians are monophasic.
The term polyphasic sleep is also used by an online community that experiments with alternative sleeping schedules in an attempt to increase productivity.
There is no scientific evidence that this practice is effective or beneficial.
Biphasic sleep,
Also referred to as segmented sleep or bimodal sleep,
Is a pattern of sleep which is divided into two segments or phases in a 24-hour period.
One classic cultural example of biphasic sleep pattern is the practice of siesta,
Which is a nap taken in the early afternoon,
Often after the midday meal.
Such a period of sleep is a common tradition in some countries,
Particularly those where the weather is warm.
The siesta is historically common throughout the Mediterranean and Southern Europe.
It is the traditional daytime sleep of China,
India,
South Africa,
Italy,
Greece,
Spain,
And,
Through Spanish influence,
The Philippines and many Hispanic American countries.
In modern times,
Fewer Spaniards take a daily siesta,
Ostensibly due to more demanding work schedules.
A separate biphasic sleep pattern is sometimes described as segmented sleep,
Involved sleeping in two phases,
Separated by about an hour of wakefulness.
This pattern was common in pre-industrial societies,
And it was most common to sleep early,
First sleep,
Wake around midnight,
And return to bed later,
Second sleep.
Along with a nap in the day,
It has been argued that this is the natural pattern of human sleep in long winter nights.
A case has been made that maintaining such a sleep pattern may be important in regulating stress.
Historian A.
Roger Ekerge has argued that before the Industrial Revolution,
Interrupted sleep was dominant in Western civilization.
Ekerge asserts that the intervening period of wakefulness was used to pray and reflect,
And to interpret dreams,
Which were more vivid at that hour than upon waking in the morning.
This was also a favorite time for scholars and poets to write uninterrupted.
He draws evidence from more than 500 references to a segmented sleeping pattern in documents from the ancient,
Medieval,
And modern world.
Other historians,
Such as Craig Koslovsky,
Have endorsed Ekerge's analysis.
Ekerge suggests that it is due to the modern use of electric lighting that most modern humans do not practice interrupted sleep.
Some have proposed that a sleep pattern based on the historical biphasic sleep schedule might be beneficial for stress or improve health markers.
Ekerge does not advocate for this,
Stating that the current uninterrupted sleep pattern is the ideal schedule for the modern world.
EXPERIMENTAL SCHEDULES Everyman Schedule The Everyman Schedule involves sleeping three hours during the night,
Core sleep,
And taking three 20-minute naps during the day.
This totals four hours of sleep in a 24-hour period.
Uberman Schedule The Uberman sleep schedule consists of a 30-minute nap every four hours,
Totaling three hours of sleep in a 24-hour period.
Other variations of this sleep pattern involve eight naps throughout the day for 20-minute sleep intervals as opposed to 30 minutes.
DIMAXION SCHEDULE Buckminster Fuller described a regimen consisting of 30-minute naps every six hours.
A short article about Fuller's nap schedule and time in 1943,
Which referred to the schedule as intermittent sleeping,
Says that he maintained it for two years,
And notes that he had to quit because his schedule conflicted with that of his business associates who insisted on sleeping like other men.
This schedule is likely the most extreme type of polyphasic sleep schedule,
Totaling only two hours of sleep in a 24-hour period.
In crisis and other extreme conditions,
People may not be able to achieve the recommended seven to nine hours of sleep per day.
Systematic napping may be considered necessary in such situations.
Claudio Stompi,
As a result of his interest in long-distance solo boat racing,
Has studied the systematic timing of short naps as a means of ensuring optimal performance in situations where extreme sleep deprivation is inevitable.
But he does not advocate ultra-short napping as a lifestyle.
Scientific American Frontiers,
PBS,
Has reported on Stompi's 49-day experiment where a young man napped for a total of three hours per day.
It purportedly shows that all stages of sleep were included.
Stompi has written about his research in his book,
Why We Nap,
Evolution,
Chronobiology,
And Functions of Polyphasic and Ultra-Short Sleep.
1992.
In 1989,
He published results of a field study in the journal Work and Stress,
Concluding that polyphasic sleep strategies improve prolonged sustained performance under continuous work situations.
In addition,
Other long-distance solo sailors have documented their techniques for maximizing wake time on the open seas.
One account documents the process by which a solo sailor broke his sleep into between six and seven naps per day.
The naps would not be placed equiphasically,
Instead occurring more densely during night hours.
The U.
S.
Military has studied fatigue countermeasures.
An Air Force report states,
Each individual nap should be long enough to provide at least 45 continuous minutes of sleep,
Although longer naps,
Two hours,
Are better.
In general,
The shorter each individual nap is,
The more frequent the naps should be.
The objective remains to acquire a daily total of eight hours of sleep.
Similarly,
The Canadian marine pilots in their trainer's handbook report that,
Under extreme condition circumstances where sleep cannot be achieved continuously,
Research on napping shows that 10 to 20 minute naps at regular intervals during the day can help relieve some of the sleep deprivation and thus maintain performance for several days.
However,
Researchers caution that levels of performance achieved using ultra-short sleep,
Short naps,
To temporarily replace normal sleep are always well below that achieved when fully rested.
NASA,
In cooperation with the National Space Biomedical Research Institute,
Has funded research on napping.
Despite NASA recommendations that astronauts sleep eight hours a day when in space,
They usually have trouble sleeping eight hours at a stretch,
So the agency needs to know about the optimal length,
Timing,
And effect of naps.
Professor David Dingus of the University of Pennsylvania School of Medicine led research in a laboratory setting on sleep schedules,
Which combined various amounts of anchor sleep,
Ranging from about four to eight hours in length,
With no nap or daily naps of up to two and a half hours.
Longer naps were found to be better,
With some cognitive functions benefiting more from napping than others.
Vigilance and basic alertness benefited the least,
While working memory benefited greatly.
Naps in the individual subjects' biological daytime worked well,
But naps in their nighttime were followed by much greater sleep inertia lasting up to an hour.
The Italian Air Force also conducted experiments for their pilots in schedules involving night shifts and fragmentation of duty periods throughout the entire day.
A sort of polyphasic sleeping schedule was studied.
Subjects were to perform two hours of activity followed by four hours of rest,
Sleep allowed.
This was repeated four times throughout the 24-hour day.
Subjects adopted a schedule of sleeping only during the final three rest periods in linearly increasing duration.
The AMI published findings that total sleep time was substantially reduced as compared to the usual seven to eight hour monophasic nocturnal sleep,
While maintaining good levels of vigilance as shown by the virtual absence of EEG microsleeps.
EEG microsleeps are measurable and usually unnoticeable bursts of sleep in the brain while a subject appears to be awake.
Nocturnal sleepers who sleep poorly may be heavily bombarded with microsleeps during waking hours,
Limiting focus and attention.
The brain exhibits high levels of the pituitary hormone prolactin during the period of nighttime wakefulness,
Which may contribute to the feeling of peace that many people associate with it.
In his 1992 study in short photoperiods,
Human sleep is biphasic,
Thomas Wehr had seven healthy men confined to a room for 14 hours of darkness daily for a month.
At first the participants slept for about 11 hours,
Presumably making up for their sleep debt.
After this,
The subjects began to sleep much as people in pre-industrial times were claimed to have done.
They would sleep for about four hours,
Wake up for two to three hours,
Then go back to bed for another four hours.
They also took about two hours to fall asleep.
Polyphasic sleep can be caused by irregular sleep-wake syndrome,
A rare circadian rhythm sleep disorder which is usually caused by neurological abnormality,
Head injury,
Or dementia.
Much more common examples are the sleep of human infants and of many animals.
Elderly humans often have disturbed sleep,
Including polyphasic sleep.
In their 2006 paper,
The Nature of Spontaneous Sleep Across Adulthood,
Campbell and Murphy studied sleep timing and quality in young,
Middle-aged,
And older adults.
They found that in free-running conditions,
The average duration of major nighttime sleep was significantly longer in young adults than in the other groups.
The paper states further,
Whether such patterns are simply a response to the relatively static experimental conditions,
Or whether they more accurately reflect the natural organization of the human sleep-wake system,
Compared with that which is exhibited in daily life,
Is open to debate.
However,
The comparative literature strongly suggests that shorter,
Polyphasically placed sleep is the rule,
Rather than the exception,
Across the entire animal kingdom.
There is little reason to believe that the human sleep-wake system would evolve in a fundamentally different manner.
That people often do not exhibit such sleep organization in daily life merely suggests that humans have the capacity,
Often with the aid of stimulants such as caffeine or increased physical activity,
To overcome the propensity for sleep when it is desirable,
Or is required to do so.
Somnolence,
Alternatively sleepiness or drowsiness,
Is a state of strong desire for sleep,
Or sleeping for unusually long periods,
And it has distinct meanings and causes.
It can refer to the usual state preceding falling asleep,
The condition of being in a drowsy state due to circadian rhythm disorders,
Or a symptom of other health problems.
It can be accompanied by lethargy,
Weakness,
And lack of mental agility.
Somnolence is often viewed as a symptom rather than a disorder by itself.
However,
The concept of somnolence recurring at certain times for certain reasons constitutes various disorders,
Such as excessive daytime sleepiness,
Shift work-sleep disorder,
And others,
And there are medical codes for somnolence as viewed as a disorder.
Sleepiness can be dangerous when performing tasks that require constant concentration,
Such as driving a vehicle.
When a person is sufficiently fatigued,
Microsleeps may be experienced.
In individuals deprived of sleep,
Somnolence may spontaneously dissipate for short periods of time.
This phenomenon is the second wind,
And results from the normal cycling of the circadian rhythm interfering with the processes the body carries out to prepare itself to rest.
The word somnolence is derived from the Latin somnus,
Meaning sleep.
Circadian rhythm,
Biological clock disorders,
Are a common cause of drowsiness,
As are a number of other conditions,
Such as sleep apnea,
Insomnia,
And narcolepsy.
The body clock disorders are classified as extrinsic,
Externally caused,
Or intrinsic.
The former type is,
For example,
Shift work-sleep disorder,
Which affects people who work nights or rotating shifts.
The intrinsic types include advanced sleep phase disorder,
ASPD,
A condition in which patients feel very sleepy and go to bed early in the evening and wake up very early in the morning.
Delayed sleep phase disorder,
DSPD,
Faulty timing of sleep,
Peak period of alertness,
The core body temperature rhythm,
Hormonal and other daily cycles,
Such that they occur a number of hours late compared to the norm,
Often misdiagnosed as insomnia.
Non-24-hour sleep-wake disorder,
A faulty body clock and sleep-wake cycle that usually is longer than,
Rarely shorter than,
The normal 24-hour period,
Causing complaints of insomnia and excessive sleepiness.
Irregular sleep-wake rhythm,
Numerous naps throughout the 24-hour period,
No main nighttime sleep episode,
And irregularity from day to day.
Sleepiness can also be a response to infection.
Some somnolence is one of several sickness behaviors or reactions to an infection that some theorize evolve to promote recovery by conserving energy while the body fights the infection using fever and other means.
Quantifying sleepiness requires a careful assessment.
The diagnosis depends on two factors,
Namely chronicity and reversibility.
Chronicity signifies that the patient,
Unlike healthy people,
Experiences persistent sleepiness which does not pass.
Reversibility stands for the fact that even if the individual goes to sleep,
The sleepiness may not be completely gone after waking up.
The problem with the assessment is that patients may only report the consequences of sleepiness,
Loss of energy,
Fatigue,
Weariness,
Difficulty remembering or concentrating,
Etc.
It is crucial to aim for objective measures to quantify the sleepiness.
A good measurement tool is the Multiple Sleep Latency Test,
MSLT.
It assesses the sleep onset latency during the course of one day,
Often from 8am to 4pm.
An average sleep onset latency of less than 5 minutes is an indication of pathological sleepiness.
A number of diagnostic tests,
Including the Epworth Sleepness Scale,
Are available to help ascertain the seriousness and likely cause of abnormal somnolence.
A power nap or cat nap is a short sleep that terminates before deep sleep,
Slow-wave sleep,
SWS.
A power nap is intended to quickly revitalize the sleeper.
A power nap combined with consuming caffeine is called a stimulant nap,
Coffee nap,
Caffeine nap,
Or nappuccino.
A power nap,
Also known as a stage 2 nap,
Is a short slumber of 20 minutes or less,
Which terminates before the occurrence of deep,
Slow-wave sleep,
Intended to quickly revitalize the napper.
The expression power nap was coined by Cornell University social psychologist,
Jay Moss.
A 20-minute nap increases alertness and motor skills.
Various durations may be recommended for power naps,
Which are short compared to regular sleep.
A short duration prevents nappers from sleeping so long that they enter the slow-wave portion of the normal sleep cycle without being able to complete the cycle.
Entering deep,
Slow-wave sleep and failing to complete the normal sleep cycle can result in a phenomenon known as sleep inertia,
Where one feels groggy,
Disoriented,
And even sleepier than before beginning the nap.
In order to attain optimal post-nap performance,
A stage 2 nap must be limited to the beginning of a sleep cycle,
Specifically sleep stages N1 and N2,
Typically 18 to 25 minutes.
Experimental confirmation of the benefits of this brief nap comes from a Flinders University study in Australia,
In which 5,
10,
20,
Or 30-minute periods of sleep were given.
The greatest immediate improvement in measures of alertness and cognitive performance came after the 10 minutes of sleep.
The 20 and 30-minute periods of sleep showed evidence of sleep inertia immediately after the naps,
And improvements in alertness more than 30 minutes later,
But not to a greater level than after the 10 minutes of sleep.
Power naps are effective even when schedules allow a full night's sleep.
