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Daytime napping is a frequent habit of many individuals, whether healthy or not, and may occur in a wide variety of contexts. There are several reasons for napping in the human adult, including prophylactic strategies or recuperative need, respectively before or after sleep loss, or even pure appetitive drive. Thus, it is of great theoretical and clinical interest to assess the impact of naps on individuals' performance, especially on cognitive functioning. As the outgrowth of a symposium held by the authors at the 5th Congress of the World Federation of Sleep Research and Sleep Medicine Societies in Cairns, Australia, September 2007, this review will specifically explore: a) the newly developed experimental daytime split-sleep schedules and their effects on recovery, compared with those deriving from a single consolidated sleep episode of equal duration; b) whether naps may be beneficial to wakefulness performance in the working context, through accurate review of "on field" studies; c) the impact of naps on cognition, in light of the very recent advances in the study of naps and memory processes; d) the main features of napping behavior in older individuals and its impact on their health and general functioning, since it is widely recognized that napping may change as a result of the aging process.
Naps, cognition and performance
Gianluca Ficca
, John Axelsson
, Daniel J. Mollicone
, Vincenzo Muto
, Michael V. Vitiello
Department of Psychology, Second University of Naples, 81100 Caserta, Italy
Karolinska Institutet, Department of Clinical Neuroscience, Section for Psychology & Osher Center for Integrative Medicine, Stockholm, Sweden
Division of Sleep and Chronobiology, Department of Psychiatry, University of Pennsylvania School of Medicine, Philadelphia, PA, USA
Departments of Psychiatry & Behavioral Sciences, Medicine (Gerontology & Geriatrics), and Biobehavioral Nursing & Health Systems, University of Washington, Seattle, WA, USA
article info
Article history:
Received 7 April 2009
Received in revised form
16 September 2009
Accepted 17 September 2009
Available online 2 December 2009
Cognitive functions
Shift work
Daytime napping is a frequent habit of many individuals, whether healthy or not, and may occur in
a wide variety of contexts. There are several reasons for napping in the human adult, including
prophylactic strategies or recuperative need, respectively before or after sleep loss, or even pure appe-
titive drive. Thus, it is of great theoretical and clinical interest to assess the impact of naps on individuals’
performance, especially on cognitive functioning. As the outgrowth of a symposium held by the authors
at the 5th Congress of the World Federation of Sleep Research and Sleep Medicine Societies in Cairns,
Australia, September 2007, this review will specifically explore: a) the newly developed experimental
daytime split-sleep schedules and their effects on recovery, compared with those deriving from a single
consolidated sleep episode of equal duration; b) whether naps may be beneficial to wakefulness
performance in the working context, through accurate review of ‘‘on field’’ studies; c) the impact of naps
on cognition, in light of the very recent advances in the study of naps and memory processes; d) the main
features of napping behavior in older individuals and its impact on their health and general functioning,
since it is widely recognized that napping may change as a result of the aging process.
Ó2009 Elsevier Ltd. All rights reserved.
Daytime napping is a frequent habit in many individuals,
whether healthy or not, and may occur in a wide variety of contexts.
Seminal research on naps, extensively reviewed in a volume by
has tried to address the regulatory mechanisms sustaining
polyphasic sleep structure, as well as to identify the determinants of
napping, on both the psychobiological and the psychosocial level.
These studies have focused on several different reasons for napping
including: recuperative need, due to prolonged wakefulness or
increased sleep pressure; prophylactic strategies, aimed to coun-
teract an expected sleep deprivation and to maintainperformance in
particular contexts such as shift work or sustained operations; and
pure appetitive drive, linked to sociocultural and individual char-
acteristics. Thus the causes of napping are likely to be multifaceted,
a picture made even more complex by the continuous interactionsof
each of these factors with the others. However, the question of what
impact napping might have on the general functioning of individ-
uals, with special regard to wakefulness performance and memory
processes, has so far received little attention.
This review seeks to raise interest in these theoretically and clin-
ically fundamental aspects of napping. It is the outgrowth of
a symposium, ‘‘The Effect of Naps on Health and Cognition’’, held by
the authors at the 5th Congress of the World Federation of Sleep
Researchand Sleep Medicine Societies in Cairns, Australia, September
2007, specifically conceived to pay thorough attention to the rela-
tionships between daytime napping and cognitive processes, in light
of the very recent advances in the study of naps, memory and
performance. Here we will examine the interrelationships of napping,
cognition and performance in four specific contexts.
First, the hypothesis that a split-sleep schedule provides more
recovery than a single consolidated sleep period of the same total
duration is examined. We will start with this particular approach
since it represents the most recent experimental contribution, after
the classical 80s studies on daytime sleep regulatory mechanisms,
to set the basis for the understanding of nap effects in ‘‘real life’’
situations. Second, the advantages and disadvantages of napping in
the work environment are examined. Third, the purported benefits
of napping for the learning of new material, either declarative (e.g.,
lists of words) or procedural (e.g., perceptual or motor tasks) are
explored, including a discussion of why daytime naps, due to their
peculiar sleep infrastructure, might represent a useful model of
memory consolidation mechanisms during sleep. Finally, the
prevalence of regular napping in the elderlyand its association with
*Corresponding author. Tel.: þ39 823 274790; fax: þ39 823 323000.
E-mail address: (G. Ficca).
Contents lists available at ScienceDirect
Sleep Medicine Reviews
journal homepage:
1087-0792/$ – see front matter Ó2009 Elsevier Ltd. All rights reserved.
Sleep Medicine Reviews 14 (2010) 249–258
sleep complaints, excessive daytime sleepiness, and mental and
physical health problems are examined, with a focus on whether
regular napping among older adults, particularly those in good
health, may be beneficial to daytime wakefulness or detrimental to
night-time sleep propensity.
Effects of split-sleep schedules on sleep stage architecture and
neurobehavioral performance
Can split-sleep enhance recuperative benefits to performance?
The idea of splitting a sleep period up into two parts of the
same total duration to provide enhanced recuperative benefits
was first posed in 1897 and came from observations about the
exponential time-course of sleep depth from measured auditory
arousal threshold.
The idea was that exponential functions are
steepest in the first half of the function (i.e., provide more
recovery per unit time invested in sleep), thus breaking sleep into
two parts would exploit this property advantageously yielding
more recovery than a single sleep period of the same total dura-
tion. In recent decades, others have reported that alertness and
performance are restored as a saturating exponential function of
total sleep,
however only a small number of studies have
directly compared split-sleep and monophasic sleep to determine
if in fact there are neurobehavioral benefits of splitting sleep into
parts. We begin with a review of the factors related to split-sleep
schedules that impact sleep architecture and neurobehavioral
performance including circadian timing of sleep, duration of prior
wakefulness, and cumulative sleep loss.
Factors related to split-sleep that affect sleep architecture
Circadian timing of sleep has been extensively examined in
experiments involving long-term temporal isolation, multi-cyclic
sleep wake schedules, and forced desynchrony. These experiments
showed that circadian phase as well as the duration of prior
wakefulness affects sleep propensity (i.e., sleep onset latencies and
sleep duration) and sleep architecture by primarily impacting rapid
eye movement (REM) sleep. In fact it has been shown that there are
certain circadian ‘‘forbidden zones’’ where nap sleep initiation
would be improbable at normal homeostatic levels.
For an
extensive review of these experiments see the review by Dijk and
Sleep loss resulting from total sleep deprivation and
chronic partial sleep deprivation has also been shown to affect
sleep propensity and sleep architecture.
Experiments about sleep
loss effects on sleep architecture are reviewed by Dinges et al.
Factors related to split-sleep that affect neurobehavioral
In order to fully characterize the impact of napping on neu-
robehavioral performance associated with split-sleep perfor-
mance, factors such as mood, cognitive performance, and motor
function must be examined across a range of homeostatic levels
resulting from both acute total sleep deprivation and chronic
partial sleep deprivation. It is known from controlled laboratory
experiments that sleep loss resulting from acute total sleep
deprivation negatively affects mood, cognitive performance, and
motor function due to an increasing sleep propensity and desta-
bilization of the wake state.
Sleep loss resulting from chronic
partial sleep deprivation progressively impacts these same factors
in a dose-response relationship with TIB across days of sleep
The duration of prior wakefulness at the time of
testing has been shown to impact performance and to interact
with circadian phase.
The important theoretical question is
whether split-sleep schedules mitigate neurobehavioral deficits
resulting from homeostatic pressure associated with sleep
restriction when compared to consolidated sleep. Sleep inertia
must also be accounted for in the interpretation of experiments
designed to measure the impact on neurobehavioral performance
of split-sleep schedules. Sleep inertia impacts neurobehavioral
performance for 2 or more hours after waking
and is most
pronounced at adverse circadian phases in the middle of the
habitual night.
It has been shown to increase in magnitude and
duration with total sleep deprivation and can be mitigated by
Finally, experimental evidence has demonstrated that
there are large, stable, trait-like differences among individuals in
the amount of daily sleep required to maintain stable levels of
In fact, individual differences in the response to
sleep loss should be considered when studying any of the above
mentioned factors related to split-sleep schedules.
Experiments that directly compare consolidated and split-sleep
We now review experiments that specifically compared
consolidated sleep with split sleep. In all of the experiments
described in this section cognitive performance was assessed using
objective measures such as a digit symbol substitution task, mental
arithmetic tasks, or simple and choice reaction times tasks. Mood
and sleepiness were assessed with subjective scales. The first
experiment considered was a within-subjects design by Nicholson
et al. that compared 8 h of continuous nocturnal sleep to a split-
sleep schedule that was comprised of two 4 h sleep periods
bisected by 10 h of nocturnal wakefulness.
No differences in
performance were detected in subsequent daytime performance
between the consolidated and split-sleep schedules. Other exper-
iments examining split-sleep compared to consolidated sleep of the
same total duration found increases in subsequent daytime
performance; however these effects were attributed to experi-
mental confounds related to differences in duration of prior
wakefulness at the time of testing.
A recent controlled labora-
tory experiment by Dinges’ group examined performance impair-
ments associated with a range of split-sleep schedules that were
comprised of restricted nocturnal sleep augmented with a daytime
nap or no nap. In order to minimize confounds related to circadian
phase and duration of prior wakefulness, data were analyzed based
on daily-average-performance to identify the functional relation-
ship between performance and nocturnal anchor sleep and diurnal
nap sleep. Tests that occurred immediately after awakening from
a nocturnal sleep or diurnal nap were not included in the daily
performance averages to avoid measuring sleep inertia effects. The
overall finding was that performance was a function of total daily
time in bed independent of whether sleep was consolidated or split
into two parts.
In terms of total sleep time and neurobehavioral
performance, it did not substantively matter whether sleep was
consolidated or scheduled in two parts.
Less is known,
however, about any health impacts of any types of split-sleep
regimen, even if this strategy of sleep would be favorable for
maintaining performance.
Effects of naps on vigilance/performance/subjective well-
being as assessed from ‘‘on field studies’’
With respect to napping in working life, most naps occur in
association with night work. Although the majority of naps seem to
be compensatory in nature (i.e., a result of sleepiness/sleep pres-
sure), the large number of naps occurring before the first night shift
demonstrate that many workers also take prophylactic naps to
reduce night-shift sleepiness.
Some studies report that up to
G. Ficca et al. / Sleep Medicine Reviews 14 (2010) 249–258250
65% of the workers take a nap before the first night shift, and this
number may increase up to 91% if preceded by a morning shift the
same day.
After the first night shift, the numbers of nap takers
are reduced, to about 10–40%,
mainly because the main sleep
bout now occurs during the day. Napping on the night shifts is
strongly affected by occupation, culture and whether the naps are
sanctioned or not.
While the literature is largely limited to
voluntary naps, night shifts are also affected by involuntary naps. It
has been estimated that the risk for unintentional sleep increases
by about 60% during night shifts.
In fact, in a larger diary study,
with self-reports of 230 train drivers and air traffic controllers, up
to 50% reported dozing off during the night shift.
Some of the
scarce objective data on involuntary naps (i.e., using ambulatory
electroencephalogram) revealed that 20% of the workers fell asleep
during the night shift, whereas none fell asleep during morning or
afternoon shifts.
Similar findings have also been shown amongst
An important finding from the former study was that many
sleep episodes were unreported by the workers themselves, sug-
gesting that falling asleep during a night shift is more common than
in self-reports.
The main reasons for reduced alertness and performance during
the night are the circadian system, promoting sleepiness and long
waking hours. Waking hours are particularly long the first night
shift, often more than 20 h. Several strategies, such as napping,
caffeine, modafinil and bright-light exposure, have been proposed
as effective countermeasures against sleepiness and performance
decrements. However, rather few studies have actually been carried
out on how effectively these countermeasures work in real life
situations. As of today, the most evidence exists for napping, and it
has been concluded that naps can alleviate shift work problems in
a reliable and inexpensive manner.
Naps and caffeine are the
most common countermeasures and a recent intervention study
has assessed their combined effect.
Below we review the studies
carried out in operational settings, particularly regarding inter-
ventions. A final section will provide some guidelines on how to
make naps more effective.
Implementation of naps to improve late night alertness
Multiple laboratory studies have demonstrated that naps from
30 min to 4 h improve alertness and performance in laboratory
conditions of simulated night-work, e.g.,
However, in most
cases, the research samples included young volunteers rather than
experienced shift/night workers and the performance tests were
most often short performance tests such as reaction time tasks
rather than work related output or safety. In an experimental study
including oil refinery shift-workers, Sallinen and co-workers
showed that naps of either 30- or 50-min taken at 01:00 h or
04:00 h improved performance at the end of the night shift.
fact that daytime sleep was somewhat impaired by the 50-min
naps suggests that longer naps may also have positive effects on
the drive home after the night shift. Naps taken before the night
shift may also improve nighttime performance and alertness.
Clearest evidence arise from studies using rather long naps,
2–3 h, which seem obvious if the aim is to have effects many hours
Effects of naturally occurring naps
In contrast to the positive findings found in laboratory studies,
naturally occurring naps have been found to relate to greater
sleepiness and poorer performance in shift workers.
This finding
supports the idea that most naps are compensatory in nature rather
than prophylactic On the other hand, in a study of 250 pilots, less
fatigue was reported amongst pilots stating that they took cockpit
naps or routinely took naps prior to overnight flights.
A recent
study of 1195 police drivers found that napping was related to
fewer car accidents.
Notably, almost 90% of the subjects took
a nap before the night shift in this extremely rapidly rotating shift
system. The unusually high degree of nap takers should be seen in
light of the fact that the night shift was preceded by several short
recovery periods and a morning shift the same day. Rather than
suggesting that prophylactic naps are effective against accidents,
these results highlight the serious consequences (substantial
increase of accident risk) for those 10% not managing a nap
between the morning and the night shifts if these occur the same
day. With the exception of this rather extreme working schedule,
there is limited knowledge as to whether naturally occurring naps
are really effective.
Implementation of naps in operational shift-work settings
Only a few studies have investigated the effects of nap inter-
ventions in operational shift-work settings. In 24 aircraft mainte-
nance workers, Purnell and co-workers found that a short 20-min
nap taken around 03:00 h had a positive effect on vigilance
performance at 07:00 h and on alertness when driving home.
study confirming possible long-term effects was carried out by
Bonnefond and co-workers. This study followed 12 industrial
workers having a one-hour nap possibility between 23:30 h and
03:30 h for a whole year.
The majority of the workers reported
reduced fatigue and improved general satisfaction. Interestingly,
the effect of the nap improved progressively over the year. These
long-term effects are rather unexpected and need to be confirmed,
particularly as no control group was included.
Napping interventions have perhaps been most successful in
extended working shifts. In a study with 20 nurses working 16 h
shifts, Takahashi and colleagues
found that a 2 h nap opportunity
improved alertness and reduced heart rate. In another study of 12-
hour shifts, it was shown that a 40-min nap opportunity at 03:00 h
had positive effects on sleepiness and driving simulator perfor-
mance at 07:30 h, indicating positive effects on alertness on the
drive home from work. As many as 90% out of the 49 physicians and
nurses actually fell asleep during the time interval allotted for the
Two studies have also introduced nap strategies in
medical interns working 30-hour shifts. Arora and colleagues
showed that the introduction of a nap-schedule with on-call
coverage resulted in more sleep and less fatigue.
In the other
study on medical interns,
advice to take naps before the night
shift was part of a larger (successful) intervention including the
reduction of maximum working hours to 16 rather than 30. Also
short 30-min cockpit naps may improve performance.
A limitation with many of the presented studies is the lack of
work output and safety measures. However, more recent studies
have included ‘‘real accidents’’,
driving simulator performance
after work
and ‘‘work logs’’.
Short tests are not similar to most
work tasks, but can still indicate where severe sleepiness and
improvements can be expected.
In real life situations, workers are free to combine several
countermeasures to improve their on-shift alertness. However, few
studies have investigated the combined effects of more than one
countermeasure in a systematic manner. In a recent study by
Schweitzer and colleagues
it was shown that an individualised
nap and caffeine intervention can be successfully introduced.
Workers at different work sites were instructed to take a 2-hour
nap at home before the first two night shifts and combine this with
a 300 mg of caffeine at the beginning of the shift. The effects
included less sleepiness and better performance at the end of the
shift. Still, further studies are required if we intend to understand
the combinatory effects of several countermeasures to maximize
alertness at crucial time points. For example, is caffeine an effective
way to reduce sleep inertia after naps on the shift?
G. Ficca et al. / Sleep Medicine Reviews 14 (2010) 249–258 251
These intervention studies have reported a series of problems
with the implementation of naps. Some workers are obviously non-
Earlier studies have proposed that almost 50% are non-
but the fact that up to 90% nap during an extended night
shift or between a morning and a night shift suggest that napping is
possible for the majority. On the other hand, intervention studies
may suffer from selection problems in that non-nappers tend to
abstain from participation; it is unclear how inclusion/exclusion of
participants in most of the studies have been carried out. Similar
selection biases may also be at play in night workers and it seems
reasonable that the capability to nap makes it possible to manage
strenuous working hours. Also sleep conditions are important and
noise has been reported as a major reason for disturbed nap sleep.
Sleep inertia is another concern as it severely interferes with
working capacity and safety in the period after awakening.
a study on nurses with 16-hour shifts it was shown that sleep
inertia may last as long as 2 h.
In addition, the beneficial effects of
brief naps may be less effective in severely sleep deprived
Another problem that affects napping in real life situa-
tions is the demand on the worker. Medical interns stated that the
main reason for not taking full advantage of their nap opportunities
were concerns for their own patients.
One of the major concerns
deriving from laboratory findings has been disturbed day sleep
after the night shift. Although this topic was not addressed in all
studies, day sleep impairment was not found in those subjects
taking relatively short, 20–30 min, naps.
Nevertheless, a slight
negative effect on subsequent day sleep should be seen as a good
sign as this also implies improved alertness on the drive home from
the night shift.
Implementation of naps to improve alertness in the afternoon
A number of laboratory studies have shown that short day-time
naps (3–30 min) may improve alertness and performance for up to
2–3 h.
Surprisingly, Brooks and Lack found that 10-min naps
were more effective than slightly longer ones.
The improvements
were immediate, hence avoiding sleep inertia, and lasted for the
remainder of the 2.5 h during which the subjects were tested.
Although most studies on brief naps are limited to subjects with
restricted sleep, typically 4–6 h of night sleep, there is some
support for brief naps to be beneficial also after normal sleep.
Takahashi and colleagues found that subjects allowed 7 h of sleep
benefited from a 15- or 45-min nap at 12:30 h – alertness was
improved more than 3 h later.
On the other hand, a small-scale
intervention study in eight Japanese industry workers showed that
a brief, 15-min, nap at 12:30 h failed to improve performance
measured at 15:00 h in workers with no prior sleep deprivation.
Perhaps the results would have been different if more than eight
participants had been included. Nevertheless, the authors reported
that the short naps improved post-nap alertness at the end of the
working week, and half of the workers continued napping the
following work week when napping was no longer obligatory.
General guidelines
In conclusion, it appears that napping should be always imple-
mented when severe sleepiness is most likely to occur. For night
workers, the worst periods coincide with the circadian trough,
around 3–6 in the morning, and on the way home from the night
shift. For the day worker, naps should be taken to avoid the after-
noon dip. In most cases, the afternoon dip is rather limited and can
often be relieved by caffeine. However, daytime napping should be
seen as a legitimate alternative for those suffering from hyper-
somnia, disturbed sleep or non-coffee drinkers.
Intervention studies clearly demonstrate that napping can
improve night shift alertness and performance. Shorter naps seem
more successful than longer naps, although there is clearly a limited
literature about the latter in operational settings. Naps before the
night shift should preferably be as long as possible, when avoidance
of sleep inertia is less important, but avoided during work time or
other periods when high performance is required. To avoid sleep
inertia, naps should not be too long (max 20–30 min), not occur at
the bottom of the circadian phase, i.e., early morning hours, nor
taken after long waking times.
An alternative to long naps may
be several short naps, but this possibility requires further
Napping seems a very important countermeasure during
extended work shifts and in operational settings,
particularly in
those contexts where safety is an important issue. Furthermore,
although most studies have been conducted in young and sleep
deprived subjects, the practical advice is that short daytime naps
are effective for those with moderately disturbed sleep and
possibly for normal sleepers. If the aim is to alleviate afternoon
sleepiness, the timing of the nap should not be too early. The
alerting effect can be further enhanced if the nap is combined with
Laboratory studies suggest that caffeine at the beginning of the
shift may also help in reducing sleep inertia from nighttime
However, further studies are needed to verify how the
use of naps and caffeine can be best combined in operational shift-
work settings. Lastly, napping recommendations should be an
integral part of all real life fatigue management.
The effect of naps on memory processes
Daytime naps as a model for the study of sleep-memory
Although the positive role of sleep for memory consolidation of
material learned before sleep (either procedural or declarative) has
been largely explored in the frame of the so-called ‘‘sleep effect’’
hypothesis (e.g.,
for extensive reviews) and is widely accepted
today, there is still an intense scientific debate on which sleep- or
memory-related factors are crucial for the effect.
Amongst these factors the role of a minimum sleep duration has
never been fully clarified.
Obviously, nap studies would be the
natural model to study the time component of sleep for memory,
but surprisingly few studies have addressed the existence of such
a ‘‘nap effect’’. Another concern is whether sleep at different
circadian phases has the same impact on memory. Likewise, rather
few (and controversial) studies have addressed this issue.
it is somewhat premature to predict whether daytime naps could
be as effective in favouring memory consolidation as normal night
sleep. This still open question of the ‘‘nap effect’’ is reviewed in
detail below, and in the ‘‘Research Agenda’’ section.
It is important to recognize that daytime naps can work as
a powerful experimental model to elucidate mechanisms through
which sleep supports memory processes. In fact, experiments using
daytime naps on memory can avoid some of the drawbacks which
affect studies of nighttime sleep. First, if naps facilitate memory,
experimental designs can use multiple naps during the day to
better understand the role of the circadian factor. Second, day-time
nap protocols may avoid severe sleepiness, which is a factor partly
hampering the validity of studies on sleep and memory when the
control group has received no night sleep. Differences of memory
recall may indeed depend on a reduction of the control group’s
recall due to sleepiness, rather than to an increase of the sleepers’
thanks to sleep. Instead, it is much easier to maintain comparable
levels of alertness when comparing, at daytime, subjects who take
naps with subjects who are ‘‘normally’’ awake and who most
probably will not experience any significant vigilance reduction.
G. Ficca et al. / Sleep Medicine Reviews 14 (2010) 249–258252
Third, as clearly explained by Backhaus and Junghanns,
effect on memory consolidation can be more confounded during
night sleep than during naps by hormone secretions, especially
cortisol and GH, influencing memory encoding and recall. Finally,
the peculiar sleep architecture of daytime naps is particularly
adequate to give hints as to the role of sleep organization (i.e., the
presence of uninterrupted NREM-REM cycles), which has been
proposed to be a crucial factor for memory consolidation.
fact, about half of the daytime naps contain a full sleep cycle, with
a short REM episode whose presence is linked to a certain
minimum amount of preceding slow wave sleep (SWS).
Any effect
on memory of this kind of naps is likely to depend on other factors
than the absolute amount of sleep states, and their percentage out
of total sleep time (TST), which are overall quite small.
Effects of daytime naps on procedural memory
Most data on naps and memory processes have been produced
by administering procedural tasks.
The study which brought new interest to the ‘‘nap effect’’ was
the one by Mednick et al.
at the beginning of the decade, who
showed how the habitual perceptual deterioration across time on
a visual discrimination task (VDT) may be prevented by taking
a nap. Deterioration over consecutive sessions was effectively
counteracted by a nap (at 14:00 h) between sessions. The authors
found that the performance at this procedural memory task was
dependent on the duration of the nap: a shorter (30-min) nap
seems to prevent the habitual deterioration across the last two
sessions, allowing the maintenance of performance, whereas
a longer (60-min) nap reverses this impairment and improves
subsequent performance. A significant difference was found in SWS
and REM sleep amount in the short versus the long naps and,
interestingly, the impact of memory consolidation processes on
sleep structure was also suggested by the increase of the amount of
SWS and REM sleep during experimental compared with baseline
Further support to the role of naps on procedural memory was
given by a later work of the same group,
reporting that naps
including both SWS and REM led to performance enhancement,
whereas naps containing only SWS only prevented deterioration
across sessions. Discussing the results of this study, the authors
proposed that the amplitude of the nap-dependent improvement
on the VDT is similar to the one they had previously seen after an
eight hour sleep night.
They suggested that SWS may be neces-
sary to stabilize performance whereas REM sleep may facilitate an
actual performance improvement.
Backhaus and Junghanns
recently reported day-time naps to
favor procedural motor learning, as indexed by performance at
a mirror-tracing task. Cajochen et al. showed positive effects of naps
on procedural memory consolidation in a serial reaction time task
(SRT), in the context of a circadian protocol.
Korman et al.,
training subjects on a finger-to-opposition sequence-learning task,
showed that an interfering reversed sequence affects the overnight
gain normally observed at this procedural task. However, a post-
training 90-minute nap is capable of reversing this interference
effect, resulting in a larger performance gain. Finally, a very recent
has shown the benefit of a midday nap (60–90 min) on
motor memory consolidation. This clear memory enhancement in
the nap condition correlated with sleep spindle density and power
at specific regional sites (centroparietal, as expected given the areas
involved in the motor task).
The only evidence in disagreement with the aforementioned
results came from a study by Tucker et al.,
assessing both
procedural and declarative performance after a short nap (about
50-min duration) administered at 13:00 h, which did not find any
significant difference between sleep and wakefulness at a proce-
dural task. Methodological factors may explain this discrepancy.
Tucker et al.,
utilized duration of naps shorter than those used in
other studies, with accompanying relevant differences in sleep
architecture, e.g., absence of REM sleep. Furthermore, Tucker et al.
adopted a very long retention interval (five hours between the
baseline recall test and the delayed cued recall test), different from
previous studies where recall was requested after a brief interval
from awakening, just enough to permit sleep inertia dissipation.
Interestingly, Milner et al.
found that although motor learning
was consolidated in a brief nap and was associated with stage 2
spindles, this occurred only for those subjects who habitually take
naps, thus introducing the theoretical issue of distinguishing nap
effects in habitual and non-habitual nappers.
Effects of daytime naps on declarative memory
Some notable evidence of a ‘‘nap effect’’ has been produced for
declarative memory. The first such study was conducted by Schoen
and Badia.
In their study, a 2-hour nap was administered to the
subjects after learning non-meaningful (nonsense syllables) and
meaningful (short stories) material. The protocol included two
subgroups, taking a nap respectively at 7:00 h and at 15:00 h, and
a control group spending the 2-hour retention period awake.
Placing the experimental naps either early in the morning or late in
the afternoon was intended to detect a time-of-day effect, and
should have also allowed to make assumptions on the role of sleep
stages, because, due to circadian and homeostatic reasons, REM
sleep is more prevalent in early morning naps, while SWS is more
prevalent in afternoon naps. Results showed a better recall for all
kinds of verbal material in both nap conditions compared with
wakefulness, with no difference in the recall between morning and
afternoon naps.
The relationship between declarative memory processes and
daytime naps has been readdressed only recently, some twenty
years after Schoen and Badia’s work. Schabus et al.
studied word-
pair association performance using a cued recall procedure, before
and after a 60-min nap at 14:00 h. Subjects were later divided in
two groups according to the composition of sleep stages: nappers
with or without SWS. No REM-nap group was included because the
short nap duration (50-min average) did not permit the REM sleep
occurrence. Results indicated that only those nappers with SWS in
their sleep showed an improvement at the declarative memory task
after the nap. Quantitative electroencephalogram (EEG) analysis
showed increased theta activity during those naps which were
associated with memory improvement.
Muto et al.
also evaluated the recall of non-associated paired
words after a daytime nap: after an immediate free recall of verbal
material, subjects took a 2-hour nap (at 14:00 h). Successive recall
tests were carried at awakening and at a further point in the early
evening (around 19:00 h). Results showed a preventive effect of
naps against the loss of the material clearly going on in the wake
condition. Interestingly, the authors, by comparing those naps
containing a minimum amount of REM sleep (10 min) to those
without REM sleep, found that only the naps containing REM were
linked to an actual improvement of memory performance. Since
the amount of REM sleep as a fuction of total sleep time was very
small, the authors concluded that the role of REM sleep for the post
nap improvement was more likely linked to the completion of the
sleep cycle than to its presence per se. This intriguing result needs
to be replicated with a larger sample, and a study employing
a larger sample is currently in preparation by the same research
In the aforementioned study by Tucker et al.,
unlike the
findings for procedural memory, subjects taking a nap improved
G. Ficca et al. / Sleep Medicine Reviews 14 (2010) 249–258 253
more at the declarative memory task than those subjects who
stayed awake. Moreover, a positive though non-significant corre-
lation was observed between improvement on the verbal task and
minutes of SWS, whereas no other sleep parameter appeared to
correlate with declarative memory. Thus, the authors were basi-
cally replicating data about the purported role of non-REM(NREM)
sleep for declarative memory processing.
Recently Lahl et al.
showed that free word recall was better
after a 60-min retention interval spent asleep rather than awake.
Differently from previous research,
no sleep parameters
correlated with recall scores. In a second experiment, the authors
tried to examine the effects of an ultra short nap (mean
TST ¼6.3 min) or a longer nap (mean TST ¼35.8 min) on verbal
material consolidation. The results indicate that even the ultra
short nap is sufficient for a better recall when compared with
wakefulness. These data are interpreted in light of a possible
facilitating effect of the mere sleep onset on memory consolidation
processes, independent of sleep stages or sleep duration. This
hypothesis had already been put forward by Tietzel and Lack
regarding the effect of sleep onset on cognitive performance
assessed through symbol-digit substitution and letter-cancellation
Schmidt et al.
investigated the effects of declarative learning
on sleep EEG activity changes during daytime sleep, under
controlled homeostatic and circadian conditions. Unrelated verbal
material was constructed with the aim of obtaining two word lists
differing in the level of concreteness, resulting in an easier and
a more difficult associative encoding condition. Immediate and
delayed cued recall were assessed respectively pre and post a 4-
hour daytime sleep. Relative to a control condition, the authors
reported an increase of the power density in the spindle frequency
range and of the density of low-frequency sleep spindles. This
increase was observed after the difficult encoding condition but not
after the easy one. Moreover EEG spectral activity changes posi-
tively correlated with memory performance changes between pre-
and post-nap test sessions. The authors concluded that the nature
of the declarative material is a determiningt factor for sleep
parameter changes.
Napping, sleep and health in older adults
The prevalence of daytime napping increases with advancing
Many factors are likely to contribute tothis, including age-
dependent changes in nighttime sleep and circadian rhythms,
co-morbid illnesses and lifestyle factors. However, the impactof the
napping of older adults on their nighttime sleep and on their
daytime functioning and health remains to be fully determined.
Here we briefly review the epidemiology of napping, the impact of
napping on nighttime sleep, and the associations between napping
and health in older adults.
Epidemiology of napping in older adults
Although prevalence rates for napping in older adults vary
widely depending on how napping behavior is defined or measured
and the population studied, older adults consistently report more
frequent napping than younger adults.
The prevalence of
napping seems to increase with advancing age within the older
population itself, with the ‘‘older old’’ typically reporting more
frequent naps than the ‘‘younger old’’.
For example, in their
analysis of the National Sleep Foundation’s ‘‘2003 Sleep in America
Poll,’’ that focused on the topic of ‘‘sleep and aging’’ in 1506 older
adults (aged 55–84 years), Foley and colleagues found that 15%
reported regular napping (4–7 times/week), ranging in prevalence
from 10% among those 55–64 years of age to 25% among those 75–
84 years of age.
MaCrae et al.
reported that in their sample of
413 older men and women (aged 60–96 years) nearly half (47.5%)
reported regular napping (>3 times/week), while 18% reported
napping more than six times per week. Finally, a recent large multi-
center study of 8101 older community-dwelling women (mean age
77.0 years), found that approximately 11% reported napping daily,
with those reporting daily napping significantly older than those
who did not.
There does not appear to be a clear gender difference in napping
among older adults. While a few studies have suggested that older
men may nap more frequently than older women,
most other
studies report no such differences.
A limitation of the survey technique employed by studies
reviewed above is that older adults often take unplanned or unin-
tentional naps, which they may not even be aware of doing (for
example, falling asleep in the evening while reading or watching
television) and therefore underestimate their napping behavior.
This problem is illustrated by the study of Yoon and colleagues
who studied napping behavior in younger and older adults using
wrist actigraphy. They reported that many older adults may have
bouts of sleep during the evening but not report them as naps,
although they also recognize that actigraphy may have difficulty
distinguishing true napping from sitting quiescently while watch-
ing television or reading.
Little work has been done examining planned versus unplanned
napping. Recent preliminary work in this area has been conducted
by Vitiello and Foley
using the National Sleep Foundation’s ‘‘2003
Sleep in America Poll,’’ of 1506 older (aged 55–84 years) adults.
They found that 36% of the sample (n ¼515) reported napping 1–7
times/week, with half of those (50.7%) reporting planned versus
unplanned napping. Being older and unmarried, excessive daytime
sleepiness, anhedonia and drinking <4 coffees/day were all
predictors of unplanned napping. However, neither measures of
nighttime sleep complaint nor of health burden predicted
unplanned napping, suggesting, albeit counter-intuitively, that
these factors have little influence on one’s plans for napping.
Causes of daytime napping in older adults
Daytime napping may be the result of a variety of causes,
including: disturbed nighttime sleep,
age-related phase
advance of circadian rhythm,
co-morbid medical and psychiatric
and lifestyle factors, or some combination of these.
However, the evidence supporting the direct contribution of any of
these factors to napping is far from conclusive. This may be because
the relationships between napping and many, and possibly most, of
these possible causal factors are likely to be bi-directional, with
disturbed sleep, advanced phase of circadian rhythms, or poor sleep
habits leading to daytime napping and daytime napping, in turn,
disrupting nighttime sleep, shifting circadian rhythm or prompting
poor sleep-related behaviors.
Impact of napping on nighttime sleep in older adults
The impact of daytime napping on nighttime sleep is unclear, as
studies in this area have yielded inconsistent findings. It is
commonly assumed that daytime napping should decrease
homeostatic sleep drive during the following night, resulting in
increased nighttime wakefulness and decreased sleep efficiency,
which would result in being tired the next day, increasing the
likelihood of napping that day with the resulting nighttime impact,
maintaining this pattern through a positive feedback process.
Several studies provide support for this conceptualization that
daytime napping can negatively impact nighttime sleep in older
adults. Monk and colleagues
found that a daytime nap shortened
G. Ficca et al. / Sleep Medicine Reviews 14 (2010) 249–258254
nighttime sleep, decreased sleep efficiency and led to earlier
morning awakening among nine healthy olderadults. Yoon et al.
observed that healthy older adults who were evening nappers had
shorter sleep durations and awakened earlier in the morning
compared to older adults who did not nap in the evening. Campbell
et al.
examined the impact of an afternoon nap on subsequent
nighttime sleep quality in healthy older adults concluding that
napping had little effect, although they reported a significant 40%
increase in sleep latency and non-significant increases in nighttime
wakefulness following napping compared to sleep following an
afternoon sedentary period. Liu and Liu
in their study of 1820
older Chinese adults reported that older age, poor perceived health,
being female, being unmarried and frequent napping were all risk
factors for insomnia.
However, other studies have not supported this relationship
between napping and sleep quality. Metz and Bunnell
132 older adults (ages 58–95) and reported that no significant
relationship was observed between any reported napping
dimension and indicators of nocturnal sleep difficulty. Rather age
had the greatest effect on napping, with older subjects taking
more frequent and longer naps; although a non-significant trend
suggested that the duration of naps might be associated with
increased difficulty initiating nocturnal sleep. Bliwise
sleep quality and related factors in 36 healthy older women, self
identifying as good or poor sleepers. While poor sleepers reported
longer sleep latencies, less total sleep time, more non-restorative
sleep, and more daytime fatigue than did good sleepers, no
differences were found between good and poor sleepers in their
number of daily naps. Mallon and Hetta,
reporting on the sleep
habits and difficulties of 876 older Swedes observed that daytime
napping was common, but not related to poor sleep. This lack of
a relationship was confirmed by Hsu
who also found no
correlation between naps and quality of sleep among 80
community-dwelling Chinese elders. Finally, Foley et al,
reporting on napping in 1506 older adults, observed that frequent
napping was associated with excessive daytime sleepiness,
depression, nocturia and pain, but not with complaints of poor
nighttime sleep.
Napping and health in older adults
Napping has been reported to be associated with increased risk
of mortality, cardiovascular disease, falls and cognitive impairment
in older adults. A number of studies have reported that napping is
related to increased risk for mortality (e.g.,
), whereas the
association between napping and cardiovascular disease is unclear,
with some studies reporting an association (e.g.,
), but not all,
) including a very recent large-sample study, which
controlled for pre-existing co-morbidites.
Brassington et al.
and Stone et al.
have both reported that napping is associated
with increased risk for falls, with Stone et al. also reporting napping
was associated with an increased risk of hip fracture. Napping may
also be associated with increased risk of cognitive impairment,
particularly compromised executive function in older women.
This last observation would seem at odds with a previous section of
this review which noted the positive impact of napping on cogni-
tion, particularly memory. However, it is important to distinguish
the potential beneficial effect of experimentally imposed naps on
memory from the cognitive impairment associated with the
frequent napping of older adults that has been shown to be asso-
ciated with increased morbidity
and mortality.
contrast clearly illustrates the complexity of the interrelationships
among napping, health and cognition, which have yet to be fully
Concluding remarks
Evidence from both laboratory experiments and ‘‘field’’ studies
appears to indicate an overall beneficial role of napping for neu-
rocognitive functions. First, all studies to date demonstrate that
correctly timed split-sleep either had a positive effect or no effect
on subsequent neurobehavioral performance supporting the
hypothesis that the restorative effects of sleep on performance may
be mantained when splitting the overall sleep episode into multiple
naps. However, whether or not performance differences between
consolidated and split-sleep schedules were observed, all of the
experiments that measured sleep with PSG reported significant
differences in the architecture of sleep stages in terms of the
proportion of slow wave sleep and REM.
This raises the
theoretical question of why split-sleep schedule induced differ-
ences in sleep architecture do not translate into differences in
subsequent neurobehavioral performance.
This result has important implications about the operational
feasibility of split-sleep schedules because, even if performance is
not enhanced by split-sleep, it provides moreflexibility to schedule
sleep in work environments that involve restricted nocturnal sleep
due to critical task scheduling.
The majority of nap studies in the work environment clearly
lead to the same conclusion. In fact, the literature on shift workers
shows that the alertness- and performance-enhancing effects of
naps during both night and afternoon shifts can be quite dramatic.
For instance, it appears that a daytime nap as short as 10-min can
improve alertness and performance for about 2.5 h in the face of
prior sleep loss, and for almost 4 h if preceded by normal sleep.
However, it remains to be determined what the best nap duration is
to achieve the most effective alerting effects, and to what extent
this might be modulated by individual variables. Moreover,
whether and how different cognitive functions (attention, working
memory, higher cognitive functions such as decision making and
planning) are differentially influenced by napping remains an open
The overview pattern of results also seems to point to a global
beneficial effect of daytime naps for memory recall. Quite
surprisingly, and differently from what has been reported in the
‘‘night sleep effect’’ literature, almost all authors report a beneficial
‘‘nap effect’’ for both procedural and declarative tasks. However,
the effect strength ranges from quite dramatic changes, even
including the actual improvement of memory performance at
to less relevant modifications, usually limited to
a reduction of the forgetting/deterioration rate,
seemingly depend on numerous factors, either related to sleep or
memory. In fact, further studies are needed to better understand:
a) what sleep features are crucial for the ‘‘nap effect’’ on memory
consolidation, clarifying the role of nap duration, sleep states
amount, sleep continuity and organization, and whether
a memory-enhancing process is triggered by sleep onset per se;
and b) whether and to what extent each memory task is differ-
entially responsive to such a nap effect.
It is also worthwhile underscoring that the effects of naps on
health and on the whole spectrum of cognitive functions might be
different for habitual compared to non-habitual nappers.
As for the relationships between napping and age, we have not
examined the effects of naps on babies’ and children’s cognitive
processes and learning abilities, since no data have been produced
on this topic apart from a pioneering study by Gomez et al.
Instead, we focused on napping behavior in the elderly. The state-
of-the-art concerning napping in older adults was summarized in
a recent Journal of the American Geriatrics Society editorial.
prevalence of spontaneous napping increases with age in adults.
This increase is likely the result of increases in nighttime sleep
G. Ficca et al. / Sleep Medicine Reviews 14 (2010) 249–258 255
disturbances, phase advance of circadian rhythms, co-morbid
medical and psychiatric illnesses and poor sleep habits. Napping
does not seem to be associated with nighttime sleep quality but
rather with excessive daytime sleepiness and medical and psychi-
atric co-morbidities. Frequent, unplanned, longer daytime naps in
older adults have the potential to negatively impact nighttime sleep
quality and may be associated with significant negative health
consequences such as increased risk of morbidity, cardiovascular
illness, falls and cognitive impairment. However, it is possible that
brief planned naps may be of benefit to the function of healthy
older adults (e.g.,
), and perhaps even older adults in poorer
We can conclude by saying that research on naps is at a very
early stage and that there is much more to learn about napping.
As suggested by Vitiello,
the field needs to move away from
relatively simplistic assessments of napping to more nuanced
assessments employing more elaborate self-reports paralleled by
objective assessment techniques, e.g., actigraphy, which will allow
for a better appreciation of the complexity of napping behavior.
Such techniques would be best employed in large, representative
samples which include both nappers and non-nappers. Only once
such quantitative assessment techniques are employed longitu-
dinally in large representative samples will a better under-
standing of the prevalence, antecedents and consequences of
napping across the full spectrum of sleep and health patterns be
Dr. Vitiello is supported by PHS grants: AG025515, AG031126,
MH072736, NR001094, and CA116400.
We wish to thank Dr. Francesca Conte and Dr. Ciro Della Monica
for their precious help in revising the manuscript.
1. Stampi C, editor. Why we nap. Evolution, chronobiology and functions of
polyphasic and ultra short sleep. Boston: Birkha
¨user; 1992.
2. Michelson E. Untersuchungen u
¨ber die Tiefe des Schlafes. Psychologische
Arbeiten 1897; 2:84–117.
3. Carskadon MA, Dement WC. Nocturnal determinants of daytime sleepi-
ness. Sleep 1982;5:S73–81.
4. Jewett ME, Dijk DJ, Kronauer RE, Dinges DF. Dose-response relationship
between sleep duration and human psychomotor vigilance and subjective
alertness. Sleep 1999;22:171–9.
*5. Lavie P. Ultra short sleep-waking schedule: gates and forbidden zones for
sleep. Electroencephalography Clin Neurophysiol 1986;63:414–25.
6. Strogatz SH, Kronauer RE, Czeisler CA. Circadian pacemaker interferes with
sleep onset at specific times each day–role in insomnia. Am J Physiol
7. Dijk DJ, Czeisler CA. Contribution of the circadian pacemaker and the sleep
homeostat to sleep propensity, sleep structure, electroencephalographic
slow waves, and sleep spindle activity in humans. Journal of Neuroscience
8. Dinges D. Probing the limits of functional capability: the effects of sleep
loss on short-duration tasks. In: Broughton RJ, Ogilvie RD, editors. Sleep,
arousal, and performance. Boston: Birkhauser; 1992. p. 177–88.
9. Van Dongen HPA, Maislin G, Mullington JM, Dinges DF. The cumulative cost
of additional wakefulness: dose-response effects on neurobehavioral
functions and sleep physiology from chronic sleep restriction and total
sleep deprivation. Sleep 2003;26:117–26.
10. Dinges DF, Baynard M, Rogers NL. Chronic sleep restriction. In: Kryger MH,
Roth T, Dement WC, editors. Principles and practice of sleep medicine. Phil-
adelphia:: W.B. Saunders; 2005. p. 67–76.
11. Durmer JS, Dinges DF. Neurocognitive consequences of sleep deprivation.
Seminars in Neurology 2005;1:117–29.
12. Belenky G, Wesensten NJ, Thorne DR, Thomas ML, Sing HC, Redmond DP,
et al. Patterns of performance degradation and restoration during sleep
Practice points
Correctly timed split-sleep, shown to have positive
effects, or at least no negative consequences on neu-
robehavioral performance, might be used for sleep-
wake schedules in work environments that involve
restricted nocturnal sleep due to critical task scheduling.
Napping is an effective important countermeasure to
maintain adequate performance levels during extended
work shifts, and in operational settings. Napping
strategies should be a natural part of programmes
having the aim to improve safety and health in the
work place.
Short day-time naps are effective on vigilance and
cognitive functions for subjects with moderately
disturbed sleep and possibly for normal sleepers.
Actually, a nap as short as 10 min can improve alertness
and performance for about 2.5 h if prior sleep loss exists
and for almost 4 h if preceded by normal sleep.
Naps appear beneficial for memory consolidation of
material newly acquired before the nap, either proce-
dural or declarative. More robust effects seem to be
given by slightly longer naps, about 60–90 min, possibly
due to the build-up of both SWS and REM sleep.
The prevalence of spontaneous napping increases with
age in adults. This increase is likely the result of
increases in nighttime sleep disturbances, phase
advance of circadian rhythms, co-morbid medical and
psychiatric illnesses and poor sleep habits.
Frequent, unplanned, longer daytime naps in older
adults have the potential to negatively impact nighttime
sleep quality and may be associated with significant
negative health consequences such as increased risk of
morbidity, cardiovascular illness, falls and cognitive
However, brief planned naps may be of benefit to the
function of healthy older adults, and perhaps even older
adults in poorer health.
Research agenda
How and to what extent the neurocognitive effects of
naps may change as a function of their circadian
placement should be explored in more details.
Further studies are needed if we aim to understand the
combinatory effects of several countermeasures to
maximize alertness at crucial time points: for instance, it
would be important to verify how the use of naps and
caffeine are best combined in operational shift-work
It is still to be understood what sleep features are crucial
for the ‘‘nap effect’’ on memory consolidation.
Lab studies could seek the effects of naps on specific
higher cognitive functions using ad-hoc paradigms and
Research on naps and cognition should include the
study of oneiric activity (i.e., dream features) during
The cognitive effects of napping at early ages should be
explored, because this might be of interest with respect
to learning processes and school performance.
More elaborate self-report paralleled by objective
assessment techniques, such as actigraphy, which allow
for a better appreciation of the complexity of napping
behavior, should be employed in large, representative
samples of older adults which include both nappers and
*The most important references are denoted by an asterisk.
G. Ficca et al. / Sleep Medicine Reviews 14 (2010) 249–258256
restriction and subsequent recovery: a sleep dose-response study. J Sleep
Res 2003;12:1–12.
13. Czeisler CA, Dijk DJ, Duffy DJ. Entrained phase of the circadian pacemaker
serves to stabilize alertness and performance throughout the habitual
waking day. In: Ogilvie RD, Harsh JR, editors. Sleep onset: normal and
abnormal processes. Washington, DC: American Psychological Association;
1994. p. 89–110.
14. Achermann P, Werth E, Dijk DJ,Borbe
´ly AA. Time course of sleep inertia after
nighttime and daytime sleep episodes. Archiv Ital Biol 1995;134:109–19.
15. Scheer F, Shea TJ, Hilton MF, Shea SA. An endogenous circadian rhythm in
sleep inertia results in greatest cognitive impairment upon awakening
during the biological night. J Biol Rhythms 2008;23:353–61.
16. Van Dongen HPA, Price NJ, Mullington JM, Szuba MP, Kapoor SC, Dinges DF.
Caffeine eliminates psychomotor vigilance deficits from sleep inertia. Sleep
17. Van Dongen HPA, Baynard MD, Maislin G, Dinges DF. Systematic interin-
dividual differences in neurobehavioral impairment from sleep loss:
evidence of trait-like differential vulnerability. Sleep 2004;27:423–33.
18. Van Dongen HPA, Vitellaro KM, Dinges DF. Individual differences in adult
human sleep and wakefulness: leitmotif for a research agenda. Sleep
19. Nicholson AN, Pascoe PA, Roehrs T, Roth T, Spencer MB, Stone BM, et al.
Sustained performance with short evening and morning sleeps. Aviat Space
Env Med 1985;56:105–14.
20. Hartley LR. Comparison of continuous and distributed reduced sleep
schedules. Quart J Exp Psychol 1974; 26:8–14.
*21. Bonnet MH, Arand DL. Consolidated and distributed nap schedules and
performance. J Sleep Res 1995;4:71–7.
22. Mollicone DJ, Van Dongen HPA, Rogers NL, Dinges DF. Response surface
mapping of neurobehavioral performance: testing the feasibility of split-
sleep schedules for space operations. Acta Astronautica 2008;63:833–40.
23. Mollicone DJ, Van Dongen HPA, Dinges DF. Optimizing sleep/wake sched-
ules in space: sleep during chronic nocturnal sleep restriction with and
without diurnal naps. Acta Astronautica 2007;60:354–61.
24. Åkerstedt T, Torsvall L, Gillberg M. Shift work and napping. In: Dinges DF,
Broughton R, editors. Sleep and alertness: chronobiological, behavioral, and
medical aspects of napping. New York: Raven Press; 1989. p. 205–20.
25. Rosa R. Napping at home and alertness on the job in rotating shift workers.
Sleep 1993;16:727–35.
*26. Garbarino S, Mascialino B, Penco MS, Squarcia S, De Carli F, Nobili L, et al.
Professional shift-work drivers who adopt prophylactic naps can reduce
the risk of car accidents during night work. Sleep 2004;27:1295–302.
27. Sallinen M, Ha
¨M, Mutanen P, Ranta R, Virkkala J, Mu
¨ller K. Sleep-wake
rhythm in an irregular shift system. J Sleep Res 2003;12:103–12.
28. Åkerstedt T, Knutsson A, Westerholm P, Theorell T, Alfredsson L,
Kecklund G. Work organization and unintentional sleep: results from the
WOLF study. Occup Env Med 2002;59:595–600.
29. Torsvall L, Åkerstedt T, Gillander K, Knutsson A. Sleep on the night shift:
24-hour EEG monitoring of spontaneous sleep/wake behavior. Psychophy-
siol 1989;26:352–8.
30. Cabon P, Bourgeois-Bougrine S, Mollard R, Coblentz A, Speyer JJ. Electronic
pilot-activity monitor: a countermeasure against fatigue on long-haul
flights. Aviat Space Environ Med 2003;74:679–82.
*31. Takahashi M. The role of prescribed napping in sleep medicine. Sleep Med
Rev 2003;7:227–35.
*32. Schweitzer PK, Randazzo AC, Stone K, Erman M, Walsh JK. Laboratory and
field studies of naps and caffeine as practical countermeasures for sleep-
wake problems associated with night work. Sleep 2006;29:39–50.
33. Bonnet MH, Arand DL. The use of prophylactic naps and caffeine to maintain
performance during a continuous operation. Ergonomics 37:1009–1020.
*34. Sallinen M, Ha
¨M, Åkerstedt T, Rosa R, Lillqvist O. Promoting alertness
with a short nap during a night shift. J Sleep Res 1998;7:240–7.
35. Macchi MM, Boulos Z, Ranney T, Simmons L, Campbell SS. Effects of an
afternoon nap on nighttime alertness and performance in long-haul
drivers. Accid Anal Prev 2002;34:825–34.
36. Petrie KJ, Powell D, Broadbent E. Fatigue self-management strategies and
reported fatigue in international pilots. Ergonomics 2004;47:461–8.
37. Purnell MT, Feyer A-M, Herbison GP. The impact of a nap opportunity
during the night shift on the performance and alertness of 12-h shift
workers. J Sleep Res 2002;11 :219–27.
38. Bonnefond A, Muzet A, Winter-Dill A-S, Bailloeuil C, Bitouze F, Bonneau A.
Innovative working schedule: introducing one short nap during the night
shift. Ergonomics 2001;44:937–45.
39. Takahashi M, Arito H, Fukuda H. Nurse’s workload associated with 16-h
night shifts. II: effects of a nap taken during the shifts. Psychiatry Clin
Neurosci 1999;53:223–5.
40. Smith-Coggins R, Howard SK, Mac DT, Wang C, Kwan S, Rosekind MR, et al.
Improving alertness and performance in emergency department physicians
and nurses: the use f planned naps. Acad Emerg Med 2006;48:596–604.
41. Arora V, Dunphy C, Chang VY, Ahmad F, Humphrey HJ, Meltzer D. The
effects of on-duty napping on intern sleep time and fatigue. Ann Intern Med
42. Lockley SW, Cronin JW, Evans EE, Cade BE, Lee CJ, Landrigan CP, et al. Effect
of reducing interns’ weekly work hours on sleep and attentional failures. N
Engl J Med 2004;351:1829–37.
43. Rosekind MR, Graeber RC, Dinges DF, Connell LJ, Rountree MS,
Spinweber CL. Crew factors in flight operations: IX. Effects of planned
cockpit rest on crew performance and alertness in Long-Haul operations.
In: Technical memorandum 103884. Moffett Field, CA: NASA; 1994.
44. Dinges DF, Whitehouse WG, Orne EC, Orne MT. The benefits of a nap during
prolonged work and wakefulness. Work & Stress 1988;2:139–53.
45. Lumley M, Roehrs T, Zorick F, Lamphere J, Roth T. The alerting effects of
naps in sleep-deprived subjects. Psychophysiol 1986;23:403–8.
46. Gillberg M, Kecklund G, Axelsson J, Åkerstedt T. The effects of a short
daytime nap after restricted night sleep. Sleep 1996;19:570–5.
47. Hayashi M, Motoyoshi N, Hori T. Recuperative power of a short daytime nap
with or without stage 2 sleep. Sleep 2005;28:829–36.
48. Brooks A, Lack L. A brief afternoon nap following nocturnal sleep restric-
tion: which nap duration is most recuperative? Sleep 2006;29:831–40.
49. Takahashi M, Fukuda H, Arito H. Brief naps during post-lunch rest: effects
on alertness, performance, and autonomic balance. Eur J Appl Physiol Occup
Physiol 1998;78:93–8.
50. Takahashi M, Nakata A, Haratani T, Ogawa Y, Arito H. Post-lunch nap as
a worksite intervention to promote alertness on the job. Ergonomics
51. Rosekind MR, Smith RM, Miller DL, Webbon LL, Co EL, Gregory KB, et al.
Alertness management: strategic naps in operational settings. J Sleep Res
1995;4(Suppl. 2):62–6.
52. Reyner LA, Horne JA. Suppression of sleepiness in drivers: combination of
caffeine with a short nap. Psychophysiol 1997 ;34:721–5.
53. Peigneux P, LaureysS, Delbeuck X, Maquet P. Sleeping brain, learning brain.
The role of sleep for memory system. Neuroreport 2001;12:A111–24.
54. Ficca G, Salzarulo P. What in sleep is formemory. Sleep Med 2004;5:225–30.
55. Barrett TR, Ekstrand BR. Effect of sleep on memory: III. Controlling for time-
of-day effects. J Exp Psychol 1972;96:321–7.
56. Nesca M, Koulack D. Recognition memory, sleep and circadian rhythms.
Can J Exp Psychol 1994;48:359–79.
57. Backhaus J, Junghanns K. Daytime naps improve procedural motor memory.
Sleep Med 2006;7:508–12.
58. Ficca G, Lombardo P, Rossi L, Salzarulo P. Morning recall of verbal material
depends on prior sleep organization. Behav Brain Res 2000;112 :159–63.
59. Salzarulo P. Etude e
´phalographique et polygraphique du som-
meil l’apre
`z midi chez le sujet normal. Electroencephal Clin Neurophysiol
1971 ;30:399–407.
*60. Mednick S, Nakayama K, Cantero JL, Atienza M, Levin AA, Pathak N, et al.
The restorative effect of naps on perceptual deterioration. Nature Neurosci
61. Mednick S, Nakayama K, Stickgold R. Sleep-dependent learning: a nap is
good as a night. Nature Neurosci 2003;6:697–8.
62. Stickgold R, James L, Hobson JA. Visual discrimination learning requires
post-training sleep. Nature Neurosci 2000;2:1237–8.
63. Cajochen C, Knoblauch V, Wirz-Justice A, Krau
¨chi K, Graw P, Wallach D.
Circadian modulation of sequence learning under high and low sleep
pressure conditions. Behav Brain Res 2004;151:167–76.
64. Korman M, Doyon J, Doljansky J, Carrier J, Dagan Y, Karni A. Daytime sleep
condenses the time course of motor memory consolidation. Nature Neu-
rosci 2007;10:1206–13.
65. Nishida M, Walker MP. Daytime naps, motor memory consolidation and
regionally specific sleep spindles. PLoS 2007;4:e341.
66. Tucker M, Yasutaka H, Wamsley E, Lau H, Chaklader A, Fishbein WA.
Daytime nap containing solely non-REM sleep enhances declarative but
not procedural memory. Neurobiology of Learning and Memory
67. Milner CE, Fogel SM, Cote KA. Habitual napping moderates motor perfor-
mance improvements following a short daytime nap. Biol Psychol
68. Schoen LS, Badia P. Facilitated recall following REM and NREM naps. Psy-
chophysiol 1984;21:299–306.
69. Schabus M, Hodlmoser K, Pecherstorfer T, Klosch G. Influence of midday
naps on declarative memory performance and motivation. Somnologie
70. Muto V, Arpaia, L, De Padova V, Russo E., Ficca G. The effect of daytime
naps on the recall of verbal material. In: Proceedings of the1st Congress of
the World Association of Sleep Medicine, Medimond:Bologna; 2005;
71. Lahl O, Wispel C, Willigens B, Petrowsky R. An ultra short episode of sleep is
sufficient to promote declarative memory performance. J Sleep Res
72. Tietzel AJ, Lack LC. The recuperative value of brief and ultra-brief naps on
alertness and cognitive performance. J Sleep Res 2002;11 :213–8.
73. Schmidt C, Peigneux P, Muto V, Schenkel M, Knoblauch V, Munch M, et al.
Encoding difficulty promotes post-learning changes in sleep spindle
activity during napping. J Neurosci 2006;26:8976–82.
74. Buysse DJ, Browman KE, Monk TH, Reynolds 3rd CF, Fasiczka AL, Kupfer DJ.
Napping and 24-hour sleep/wake patterns in healthy elderly and young
adults. J Am Geriatr Soc 1992;40:779–86.
*75. Foley DJ, Vitiello MV, Bliwise DL, Ancoli-Israel S, Monjan AA, Walsh JK.
Frequent napping is associated with excessive daytime sleepiness,
depression, pain and nocturia in older adults. American J Geriatr Psychiatry
G. Ficca et al. / Sleep Medicine Reviews 14 (2010) 249–258 257
76. Metz ME, Bunnell DE. Napping and sleep disturbances in the elderly. Fam
Pract Res J 1990;10:47–56.
77. McCrae CS, Rowe MA, Dautovich ND, Lichstein KL, Durrence HH, Riedel BW,
et al. Sleep hygiene practices in two community dwelling samples of older
adults. Sleep 2006;29:1551–60.
78. *Stone KL, Ewing SK, Lui LY, Ensrud KE, Ancoli-Israel S, Bauer DC, et al. Self-
reported sleep and nap habits and risk of falls and fractures in older
women: the study of osteoporotic fractures. J Am Geriatr Soc
79. Gislason T, Reynisdottir H, Kristbjarnarson H, Benediktsdottir B. Sleep
habits and sleep disturbances among the elderly–an epidemiological
survey. J Intern Med 1993;234:31–9.
80. Mallon L, Hetta J. A survey of sleep habits and sleeping difficulties in an
elderly Swedish population. Ups J Med Sci 1997 ;10 2:185–97.
81. Yoon IY, Kripke DF,Youngstedt SD, Elliott JA. Actigraphy suggests age-related
differences in napping and nocturnal sleep. J Sleep Res 2003;12:87–93.
82. Vitiello MV, Foley DJ. Predictors of planned and unplanned napping in
older adults. Sleep 2007;30:A105–6.
83. Ohayon MM. Epidemiology of insomnia: what we know and what we still
need to learn. Sleep Medicine Reviews 2002;6:97–111.
*84. Ohayon MM, Carskadon MA, Guilleminault C, Vitiello MV. Meta-analysis of
quantitative sleep parameters from childhood to old age in healthy indi-
viduals: developing normative sleep values across the human lifespan.
Sleep 2004;27:1255–73.
85. Monk TH. Aging human circadian rhythms: conventional wisdom may not
always be right. J Biol Rhythm 2005;20:366–74.
86. Monk TH, Buysse DJ, Carrier J, Billy BD, Rose LR. Effects of afternoon ‘‘siesta’’
naps on sleep, alertness, performance, and circadian rhythms in the elderly.
Sleep 2001;24:680–7.
87. Campbell SS, Murphy PJ, Stauble TN. Effects of a nap on nighttime sleep and
waking function in older subjects. J Am Geriatr Soc. 2005;53:48–53.
88. Liu X, Liu L. Sleep habits and insomnia in a sample of elderly persons in
China. Sleep 2005;28:1579–87.
89. Bliwise NG. Factors related to sleep quality in healthy elderly women.
Psychol Aging 1992;7:83–8.
90. Hsu HC. Relationships between quality of sleep and its related factors
among elderly Chinese immigrants in the Seattle area. J Nurs Res
91. Bursztyn M, Ginsberg G, Hammerman-Rozenberg R, Stessman J. The siesta
in the elderly: risk factor for mortality? Arch Intern Med 1999;159:1582–6.
*92. Newman AB, Spiekerman CF, Enright P, Lefkowitz D, Manolio T,
Reynolds CF, et al. Daytime sleepiness predicts mortality and cardiovas-
cular disease in older adults. The cardiovascular health study research
group. JAm Geriatr Soc 2000;48:115–23.
93. Bursztyn M, Ginsberg G, Stessman J. The siesta and mortality in the elderly:
effectof rest without sleep anddaytime sleep duration.Sleep 2002;25:187–91.
94. Bursztyn M, Stessman J. The siesta and mortality: twelve years of
prospective observations in 70-year-olds. Sleep 2005;28:345–7.
*95. Stone KL, Ewing SK, Ancoli-Israel S, Ensrud KE, Redline S, Bauer DC, et al.
Self-Reported sleep and nap habits and risk of mortality in a large cohort of
older women. J Am Geriatr Soc; 2009 Feb 10 [Epub ahead of print].
96. Trichopoulos D, Tzonou A, Christopoulos C, Havatzoglou S, Trichopoulou A.
Does a siesta protect from coronary heart disease? Lancet 1987;2:269–70.
97. Kalandidi A, Tzonou A, Toupadaki N, Lan SJ, Koutis C, Drogari P, et al. Acase-
control study of coronary heart disease in Athens. Greece. Int J Epidemiol
98. Naska A, Oikonomou E, Trichopoulou A, Psaltopoulou T, Trichopoulos D.
Siesta in healthy adults and coronary mortality in the general population.
Arch Intern Med 2007;167:296–301.
99. Brassington GS, King AC, Bliwise DL. Sleep problems as a risk factor for falls
in a sample of community-dwelling adults aged 64–99 years. J Am Geriatr
Soc 2000;48:1234–40.
100. Blackwell T, Yaffe K, Ancoli-Israel S, Schneider JL, Cauley JA, Hillier TA, et al.
Poor sleep is associated with impaired cognitive function in older women:
the study of osteoporotic fractures. J Gerontol A Biol Sci Med Sci
101. Go
`mez RL, Bootzin RR, Nadel L. Naps promote abstraction in language-
learning infants. Psychol Sci 2006;17:670–4.
102. Vitiello MV. We have much more to learn about napping in older adults
(Editorial). J Am Geri Soc. 2008;56:1753–5.
G. Ficca et al. / Sleep Medicine Reviews 14 (2010) 249–258258
... A self-assessment version of the Morningness-Eveningness Questionnaire [42,43], including 19 multiplechoice questions regarding sleep habits and preferences with a total score ranging from 16 to 86, was used to assess chronotype. The nurses were classified into five categories based on the total score: "definite morning type (total score: 70-86)," "moderate morning type (59)(60)(61)(62)(63)(64)(65)(66)(67)(68)(69)," "intermediate type (42)(43)(44)(45)(46)(47)(48)(49)(50)(51)(52)(53)(54)(55)(56)(57)(58)," "moderate evening type (31)(32)(33)(34)(35)(36)(37)(38)(39)(40)(41)," and "definite evening type (16)(17)(18)(19)(20)(21)(22)(23)(24)(25)(26)(27)(28)(29)(30)." Data on sleep-related habits were obtained using a questionnaire comprising frequency of caffeine intake, daily time spent on electronic devices (e.g., cellular phone, smartphone, tablet) during the day and before bedtime. ...
... Adjusted odds ratios (aORs) and 95% confidence intervals (CIs) were then calculated. Awakening duration until nap breaks, the interval from the last awakening time before the night shift to the start time of nap breaks, was used as a covariate to adjust the homeostatic sleep pressure [50,51]. ...
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For nurses working long night shifts, it is imperative that they have the ability to take naps to reduce fatigue, and that an appropriate environment is prepared where such naps can be taken. We verified the effects of 90 min napping on fatigue and the associated factors among nurses working 16-h night shifts. We investigated 196-night shifts among 49 nurses for one month. Wearable devices, data logging devices, and questionnaires were used to assess nap parameters, fatigue, and environmental factors such as the napping environment, ways of spending breaks, and working environment. Nurses who nap at least 90 min on most night shifts had more nursing experience. Multivariable logistic regression analysis showed that the environmental factors significantly associated with total nap duration (TND) ≥ 90 min were noise, time spent on electronic devices such as cellphones and tablets during breaks, and nap break duration. The night shifts with TND ≥ 90 min showed lower drowsiness after nap breaks and less fatigue at the end of night shift compared to those with TND < 90 min. Nurses and nursing managers should recognize the importance of napping and make adjustments to nap for at least 90 min during long night shifts.
... In this context, napping, tied to the incentive to work from home, the increasing global use of electronic devices, and the shortening of nighttime sleep with societal development, can be reassessed as a modern phenomenon [16]. Some of the research data related to napping have concluded that it is helpful in optimizing memory, improving learning ability and mood, as well as being a healthful behavioral habit [17,18]. However, numerous recent studies have linked siestas to unfavorable health consequences, including respiratory disorders, cardiovascular disorders, metabolic syndrome, cancer, depression, and even death [19][20][21][22][23]. ...
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Introduction To date, many studies have shown a link between siesta and cardiovascular events. Little is known regarding the connection between siesta and brachial-ankle pulse wave velocity (baPWV) levels, even though baPWV can determine the degree of atherosclerosis and vascular stiffness. Thus, we examined the relationship between siesta time and baPWV in a cross-sectional study. Methods Interviews, physical examinations, lab testing, and electron beam computed tomography were all part of the baseline evaluation for participants aged older than 35. Baseline data were compared for 3 different siesta habits: irregular or no siestas, daily short siestas (1 h or less), and daily long siestas (> 1 h). Utilizing logistic regression models and multivariate linear regression, the link between siesta time and baPWV was determined. Results Among all 6566 participants, the different siesta groups had a significant difference of the degrees of AS (P < 0.001). The same outcome was true for both males (P < 0.001) and females (P < 0.001). Numerous cardiovascular risk variables and markers of subclinical atherosclerosis were positively correlated with daily extended siestas. Results from the fully adjusted model showed that long siestas (> 60 min, OR = 1.18, 95%CI: 1.06–1.31, P = 0.002) were linked to a more severe level of the baPWV. For age or gender stratification, we found significant differences between non-siesta and > 60 min siesta groups. Multiple linear regression analysis revealed a positive connection between siesta duration and baPWV (β = 0.197, P = 0.038). Conclusions An elevated risk of atherosclerosis was shown to accompany prolonged siestas. These results need to be followed up on with prospective studies and additional lab work.
... Given the prevalence of sleep curtailment in modern society, scheduled napping is increasingly gaining traction as a remedy to counter the detrimental cognitive effects of chronic short nocturnal sleep [1]. Studies have shown that afternoon naps scheduled to coincide with a period of higher sleep propensity [2] can reduce homeostatic sleep pressure [3,4] and improve vigilance and memory [5][6][7]. However, pressure to participate in other activities vies with napping for this purpose [8]. ...
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Study objectives: To determine how mid-afternoon naps of differing durations benefit memory encoding, vigilance, speed-of-processing (SOP), mood, and sleepiness; to evaluate if these benefits extend past 3 h post-awakening and to examine how sleep macrostructure during naps modulate these benefits. Methods: Following short habitual sleep, 32 young adults underwent 4 experimental conditions in randomized order: wake; naps of 10min, 30min and 60min duration verified with polysomnography. A 10-min test battery was delivered at a pre-nap baseline, and at 5min, 30min, 60min and 240min post nap. Participants encoded pictures 90min post-nap and were tested for recognition 210min later. Results: Naps ranging from 10-60mins increased positive mood and alleviated subjective sleepiness up to 240min post-nap. Compared to wake, only naps of 30min improved memory encoding. Improvements for vigilance were moderate, and benefits for SOP were not observed. Sleep inertia was observed for the 30min to 60min naps but was resolved within 30mins after waking. We found no significant associations between sleep macrostructure and memory benefits. Conclusions: With short habitual sleep, naps ranging from 10-60mins had clear and lasting benefits for positive mood and subjective sleepiness / alertness. Cognitive improvements were moderate, with only the 30min nap showing benefits for memory encoding. While there is no clear 'winning' nap duration, a 30min nap appears to have the best trade-off between practicability and benefit.
... Naps are short periods of sleep that occur outside a longer main nocturnal sleep period [1]. The use of naps to counter the cognitive consequences of short sleep [2,3], is increasingly being expanded to also being a tool to enhance learning by exploiting its positive effects on memory and learning [4,5]. As investigations extend over a wide range of nap characteristics and cognitive domains, a review of the current state-of-the-art is timely to update advisories on the role of napping for improving sleep and cognitive health. ...
Naps are increasingly considered a means to boost cognitive performance. We quantified the cognitive effects of napping in 60 samples from 54 studies. 52 samples evaluated memory. We first evaluated effect sizes for all tests together, before separately assessing their effects on memory, vigilance, speed of processing and executive function. We next examined whether nap effects were moderated by study features of age, nap length, nap start time, habituality and prior sleep restriction. Naps showed significant benefits for the total aggregate of cognitive tests (Cohen's d = 0.379, CI95 = 0.296–0.462). Significant domain specific effects were present for declarative (Cohen's d = 0.376, CI95 = 0.269–0.482) and procedural memory (Cohen's d = 0.494, CI95 = 0.301–0.686), vigilance (Cohen's d = 0.610, CI95 = 0.291–0.929) and speed of processing (Cohen's d = 0.211, CI95 = 0.052–0.369). There were no significant moderation effects of any of the study features. Nap effects were of comparable magnitude across subgroups of each of the 5 moderators (Q values = 0.009 to 8.572, p values > 0.116). Afternoon naps have a small to medium benefit over multiple cognitive tests. These effects transcend age, nap duration and tentatively, habituality and prior nocturnal sleep.
... Daytime napping, a sleep habit of some, can also be evidence of inadequate nocturnal sleep (Ficca et al. 2010). Although it can help offset cognitive impairments associated with short nighttime sleep, napping is not a social norm for older students and working adults in Western societies (Alger et al. 2019), and it has diminished in many East Asian, Latin, Mediterranean, and Middle-Eastern countries. ...
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The restorative function of sleep is shaped by its duration, timing, continuity, subjective quality, and efficiency. Current sleep recommendations specify only nocturnal duration and have been largely derived from sleep self-reports that can be imprecise and miss relevant details. Sleep duration, preferred timing, and ability to withstand sleep deprivation are heritable traits whose expression may change with age and affect the optimal sleep prescription for an individual. Prevailing societal norms and circumstances related to work and relationships interact to influence sleep opportunity and quality. The value of allocating time for sleep is revealed by the impact of its restriction on behavior, functional brain imaging, sleep macrostructure, and late-life cognition. Augmentation of sleep slow oscillations and spindles have been proposed for enhancing sleep quality, but they inconsistently achieve their goal. Crafting bespoke sleep recommendations could benefit from large-scale, longitudinal collection of objective sleep data integrated with behavioral and self-reported data. Expected final online publication date for the Annual Review of Psychology, Volume 74 is January 2023. Please see for revised estimates.
... In contrast, a small number of studies also found no beneficial effects of daytime napping on declarative memory consolidation (Backhaus & Junghanns, 2006;Schmidt et al., 2006). Evidence has shown that the nap-dependent improvement in performance would depend on the sleep stages and the duration of sleep (Ficca, Axelsson, Mollicone, Muto, & Vitiello, 2010), that is, either the positive correlation between the amount of SWS and performance on declarative memory (Axmacher, Haupt, Fernandez, Elger, & Fell, 2008;Tucker et al., 2006), or the contribution of REM sleep to declarative memory consolidation (Batterink, Westerberg, & Paller, 2017) was revealed. Thus, the relatively short duration of SWS or the absence of REM sleep employed in the current study might explain the failure of benefitting the consolidation of declarative memory. ...
The relationship between sleep and memory consolidation has not been fully revealed. The current study aimed to investigate how a brief afternoon nap contributed to the consolidation of declarative and procedural memory by exploring the relationship between sleep characteristics (i.e., the durations of sleep stages and slow oscillation, slow-wave activity, and spindle activity extracted from sleep) and task performance and the relationship between delta, theta, alpha, and beta bands extracted from wake during task performance and task performance. Twenty-three healthy young adults were recruited to learn a paired associates learning task and a sequential finger-tapping task with easy and difficult levels and be tested for memory performance before and after the intervention (i.e., an about 30-min nap or stay awake). Electroencephalogram (EEG) signals were recorded during the whole experiment. Results revealed that a short afternoon nap improved movement speed for the procedural memory task, regardless of the task difficulty, but unaffected the performance on the declarative memory task. Besides, the improvement in movement speed for the easy procedural memory task was positively correlated with slow-wave activity (SWA) during non-rapid-eye-movement (NREM) sleep but negatively correlated with slow oscillation and spindle activity during sleep stage 2 and NREM sleep, and the improvement in the difficult procedural memory task correlated positively with SWA during NREM sleep. Moreover, performance on the easy declarative and procedural memory tasks was negatively correlated with the relative power of alpha or theta; whereas the alpha band was positively correlated with the difficult declarative memory performance. These findings suggested that a brief afternoon nap with NREM sleep would benefit procedural memory consolidation but not declarative memory; such contribution of napping to memory consolidation would be either explained by the sleep characteristics or physiological arousal during performing tasks; task difficulty would moderate the relationship between performance on the declarative memory task and EEGs during task performance.
... This raises the possibility that the sleepedeception relationship might show some curvilinearity. Conversely, naps have shown some promise in reducing moderate daytime sleepiness [66]. Could naps move individuals far enough down the sleepiness curve to counteract deception? ...
Unhealthy sleep is a modern epidemic, and recent research has linked it to unethical behaviors like deception. Yet, scholars are also starting to examine factors that could curtail unhealthy sleep and its consequences. The current paper reviews evidence that indirectly implies or directly documents a relationship between unhealthy sleep and deception, detailing critical mediators and moderators. It concludes with a discussion of the many intriguing research avenues arising from this nascent literature, each with eminent relevance in a sleep-deprived world.
Sleep is a universal, biological need, foundational to human biology. Poor sleep health is associated with worse physical performance, greater likelihood of illness, injury risk, decreased recovery, metabolic dysregulation, cardiovascular risk, cognitive dysfunction, worse mental health, and decreased longevity. Most outcomes that are important for athletes are at least partially impacted by sleep. Yet, sleep-related problems are common among athletes, under-recognized, and under-addressed. This chapter will outline the basics of sleep and sleep–wake regulation, how it is measured, and how sleep problems arise. It will also describe different types of sleep disorders, describing presentation and symptoms, as well as treatment approaches. Then, the relationship between sleep and outcomes in athletes will be discussed, as well as strategies for developing a robust sleep health program within an athletics organization. Finally, recommendations for athletics programs are provided.KeywordsSleepInsomniaSleep disordersSleep deprivationMeasurementWearables
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Although recent research showed the positive impact of daytime naps on procedural memory, their effects on declarative memory have been so far almost completely neglected. The aim of the present study is to investigate whether a daytime nap can have a facilitating effect on the recall of verbal material and, if so, which sleep characteristics play a role. Our data show that performance at the declarative task was globally better after a two-hours nap than after the same retention interval spent awake. This resulted from a maintenance of the memory scores over three successive recall tests (14, 16, 19h) in the former condition, compared to the worsening found in the latter. On one side, this might be partly dependent on the beneficial effect of naps on alertness as shown by the subjective sleepiness scores at the three tests: however, differences observed between naps with and without REM sleep suggest that there is an influence of diurnal sleep episodes on memory consolidation which could be related to the presence of both sleep states.
Sleep in shift work has been studied extensively in regular shift systems but to a lesser degree in irregular shifts. Our main aim was to examine the sleep-wake rhythm in shift combinations ending with the night or the morning shift in two irregular shift systems. Three weeks' sleep/work shift diary data, collected from 126 randomly selected train drivers and 104 traffic controllers, were used in statistical analyses including a linear mixed model and a generalized linear model for repeated measurements. The results showed that the sleep-wake rhythm was significantly affected by the shift combinations. The main sleep period before the first night shift shortened by about 2 h when the morning shift immediately preceded the night shift as compared with the combination containing at least 36 h of free time before the night shift (reference combination). The main sleep period before the night shift was most curtailed between two night shifts, on average by 2.9 and 3.5 h among the drivers and the controllers, respectively, as compared with the reference combination. Afternoon napping increased when the morning or the day shift immediately preceded the night shift, the odds being 4.35-4.84 in comparison with the reference combination. The main sleep period before the morning shift became 0.5 h shorter when the evening shift preceded the morning shift in comparison with the sleep period after a free day. The risk for dozing off during the shift was associated only with the shift length, increasing by 17 and 35% for each working hour in the morning and the night shift, respectively. The results demonstrate advantageous and disadvantageous shift combinations in relation to sleep and make it possible to improve the ergonomy of irregular shift systems.
This authoritative guide to sleep medicine is also available as an e-dition, book (ISBN: 1416003207) plus updated online reference! The new edition of this definitive resource has been completely revised and updated to provide all of the latest scientific and clinical advances. Drs. Kryger, Roth, and Dementand over 170 international expertsdiscuss the most recent data, management guidelines, and treatments for a full range of sleep problems. Representing a wide variety of specialties, including pulmonary, neurology, psychiatry, cardiology, internal medicine, otolaryngology, and primary care, this whos who of experts delivers the most compelling, readable, and scientifically accurate source of sleep medicine available today. Includes user-friendly synopses of important background information before all basic science chapters. Provides expert coverage of narcolepsy * movement disorders * breathing disorders * gastrointestinal problems * neurological conditions * psychiatric disturbances * substance abuse * and more. Discusses hot topics such as the genetic mechanisms of circadian rhythms * the relationship between obesity, hormones, and sleep apnea * sleep apnea and arterial hypertension * and more. Includes a new section on Cardiovascular Disorders that examines the links between sleep breathing disorders and cardiovascular abnormalities, as well as the use of sleep related therapies for congestive heart failure. Provides a new section on Womens Health and Sleep Disorders that includes information on the effects of hormonal changes during pregnancy and menopause on sleep. Features the fresh perspectives of 4 new section editors. Employs a more consistent chapter organization for better readability and easier navigation.
Elderly women in subjectively good health-free of acute illness and major sleep pathologies-who were self-identified as good (n = 22) and poor (n = 16) sleepers were compared on measures of physical health, psychological symptoms, psychosocial status, and life-style. Poor sleepers reported longer sleep latencies, less total sleep time, more nonrestorative sleep, and more daytime fatigue than did good sleepers. Sleep recordings confirmed subjective reports, with shorter total sleep times and trends for lower sleep efficiency, longer sleep latencies, and more wake-after-sleep onset among women with subjective poor sleep. Poor sleepers also were more frequent users of sedative-hypnotic medications in the past. Current medication use, alcohol and caffeine use, daytime napping, and exercise were equivalent in both groups. Psychosocial status failed to discriminate groups. Poor sleepers reported significantly more psychological symptoms than did good sleepers. The levels of both psychological symptoms and sleep disturbance were mild.