Life Span changes in Sleep
Aims
To know and understand research into life
span changes in sleep
Key concepts
• A developmental approach
• Sleep quality reduction
– REM reduction
• 90,60,25,20,10
– SWS 3 and 4 reduction
• GH reduction
• Cultural differences
• Circadian phase disorders
– Chronotypes
Adults
• Redline (2004) meta analysis shows us that as
we age:
– Total sleep decreases
– Time to get to sleep increases
– Night time wakings increases
– Feeling refreshed on waking increases
– Feeling sleepy in the day increases
– Daytime naps increase
Age related variations
Life span changes
Life span changes in sleep
• REM sleep in premature children is about 80% of total
sleep time. In newborns, REM sleep counts for
50/60% of total sleep, and falls to about 25% for
children. This falls further to 20% for young adults,
whereas older adults (60s-70s) REM is about 10%.
*Use owls and larks to show how age causes the
changes to sleep patterns; these are age related
circadian phase disorders/fluctuations)
*REM changes linked to Brain development and
memory consolidation
Interestingly reduction to SWS34
• In humans and animals there is a reduction in sleep
stages S3 SWS and S4 SWS. By 60 we sleep less than
half we did at 20 in these stages. This is also true of
those suffering from (early) senile dementia.
• Therefore it is possible that the loss of these stages
rather than the loss of sleep overall is related to a
reduction in the ability to store new memories.
• However there are still people in their 80’/90s that
lack S3 and S4 but are still cognitively unimpaired.
• Also we must remember that McCrae et al. (2005)
have uncovered evidence that elderly people
actually sleep longer hours than they report, and
that part of this is because they frequently
experience micro sleeps (cat naps) during the day.
Older adults Adults
Teenagers
Children
Infants
Older adults
Adults
Teenagers
Children
Sleep Phase
advances are
common
(similar to the
genetic
chronotype
FASPS)
90 min cycle
5 cycles
-Continuous
sleep
-REM increases
in each cycle
Experience sleep
Phase delay due
to age related
hormone changes
- owls
(DSPS)
Wake up a lot
Immediate
deep sleep
Circadian shift
phase disorder–
owls
Micro sleeps
during the day;
make up lost
sleep at night
sleep walking
in
3% of adults
Cultural
differences:
between and
within cultures
REM sleep is
10% of total
sleep time in
60/ 70 year olds
young adults
sleep 20% of
total sleep
time in REM
There is a
25% of total
similar
sleep time is in
reduction in
REM
sleep duration
in 11-16 years in
all cultures
Wet dreams are
a feature
Sleep walking
(under-developed
sleep control
mechanisms)
Infants
60 min cycle
Quiet=NRem
Active=REM
-Non –continuous sleep
-6 months circadian
rhythm est.
It takes 20 minutes
before they enter deep
sleep
Sleep
walking/terrors
20% of children
Pages 18-19
REM sleeps counts for
50/60% of total sleep
time
Premature babies
sleep 80% of total
sleep time in REM –
possibly due to brain
dev.
Problems with Self reporting data
Unreliable
Subjective
REM
reduction
Infant sleep
• Newborns spend about 17 hours a day
sleeping.
– About 50% in REM sleep.
– Sleep is interrupted every 3-4hours
• By 6 months babies sleep longer
– Sleep periods extend to about 6hrs and tend to be
more associated with night time
– May be influenced by parents
Toddlers
• By 12 months
– Total sleep has declined to
about 13 hours (Sheldon
1996)
– REM sleep has decreased
to 4-5 hours
• 2-3 years
– Day time naps still
common
A point to note is
that there is a
similar reduction in
sleep duration in 1116 years in all
cultures
We must avoid culturally biased conclusions!
What does the graph tell us?
Even within a culture there
are great differences across ages
400,000
Page 19 ... Final paragraph: conclusion
We cannot generalise from culture to culture; or from
age group to age group within a specific culture.
• Adolescent sleep has been a very popular subject lately.
People are questioning the fact that it may be true that
their teenage sons and daughters may need more sleep
than they did as a child, that they are not turning into lazy,
sleepy young adults by choice.
• Sometime in late puberty, the body secretes the sleeprelated hormone melatonin at a different time than it
normally does.
– This changes the circadian rhythms that guide a person's
sleep-wake cycle. For instance, if you told your teen to go to
bed at 10 p.m., she may end up staring at the ceiling until 1 or
2 a.m. waiting to fall asleep. At about 7:30 p.m. a teen feels
wide awake and fully alert, unlike an adult who is starting to
"wind down" and feel sleepier as the evening progresses so
that at 10 p.m. the adult is ready to go to bed. The teen-agers
"wind down" time takes place much later. Owls – Phase delay.
Changes Are Taking Place
• Studies show that the changes taking place in their
bodies requires more sleep and they may be
physically challenged to getting up early in the
morning.
• Their internal biological clock may slow down in
adolescence. That can account for not their being
sleepy until 2 a.m. To think that their child, who once
awoke at the crack of dawn and was eager to watch
cartoons even on Saturday mornings has now by
choice, turned into a lazy, sleepy, young adult who
wouldn't wake up in the morning if a bomb went off
in the next room, is trying to undermine their
authority in some way.
Other comments
• Adolescent brains are going through a critical
phase of development.
• Sleep is crucial to ensure healthy development
• Hansen (2005) suggests that school start times
should be adjusted to accommodate this. E.g.
no tests before 10am!
Adolescents
Wolfson &
Carskadon
(1998)
Pagel (2007)
• Crowley (2007) showed that adolescent sleep
patterns vary with the school year.
– Circadian rhythms are reset on Mondays which result
in symptoms of jet-lag (where the EP is
desynchronised).
• Carskadon (1998) found A grade 16-18yr olds
slept an average of an hour a day longer than
other students.
• During adolescence the brain is going through a
critical phase of development and cognitive
development. Sleep is crucial in ensuring that
these changes occur efficiently.
RWA: Future Recommendations – start college later in the
morning to cater for teenagers
Other factors that may impact sleep
patterns?
• Adolescents: The cause is usually the social
changes such as
• Sleeping longer at weekends.
• Staying up later.
• Reduced parental influence.
• Several environmental factors are also
responsible for changes in sleep……..
Other comments ...
• Poor sleep is associated with depression, poor
memory and greater use of over-the-counter
sleep remedies.
• Healthy adults much less likely to nap.
• Ancoli-Israel (2008) suggests poor sleep in
elderly may be due to ill health and
medication rather than aging itself.
Evaluation: Objective measurements
• Research into lifespan changes in sleep has been
conducted in numerous sleep laboratories
throughout the world, and the changes noted in
the different stages of sleep involving both the
quantity and the quality of sleep have been
replicated and are reasonably well established.
This is particularly true with respect to normal
infant sleep because since the 1970s the US
National Institute of Health has conducted
exhaustive research into this topic in the hope of
discovering the cause of Sudden Infant Death
Syndrome (SIDS), often referred to as ‘cot death’
(Dement, 1999).
Reporting difficulties
• There are questions as to the external validity of laboratory-based
research into sleep.
• Borbely et al (1981) questioned adults aged 65-83 years of age on
their sleeping habits. They found that as many as 60% of them
reported taking frequent daily naps. While the elderly do find that
their sleep becomes more interrupted, they continue to need
about the same amount of sleep as they did in early adulthood,
hence the need for daytime naps.
• These naps may account for the reduced sleep times recorded at
night and it remains unclear whether total sleeping time always
decreases in elderly people. There has also been a lack of research
into normal sleep among the middle-aged.
• Dement (1999) believes that this is because they are so busy
trying to raise families, succeed at work and so on, that they find
less time to volunteer for sleep laboratory research. Ironically,
their busy lives suggest that they are precisely the group that
should be researched since it is also the time when the greatest
number of sleep problems occur.
Methodological problems
• A major problem with all sleep research involves
the measurement of sleep. In order to measure
the physiology of sleep in a laboratory, willing
participants have to be connected to a number
of electrodes. This must affect the quality and
quantity of sleep that they experience. For this
reason, it is often preferred if participants can
spend more than one night in the sleep
laboratory so that they may get more used to
sleeping with the equipment and wires in place.
Under researched co-sleep
• There are numerous factors that affect the quality
and quantity of sleep experienced. Work patterns,
children, aches and pains, and medication can all
affect sleep patterns. One factor that is underresearched is the effect of sleeping with a
partner. For many people the majority of their
sleeping lives are spent sharing a bed with a
partner and yet the effects of co-sleep are underresearched.
• This area of research would have practical
difficulties in a laboratory but co-sleep patterns
may be both qualitatively and quantitatively
different from sleeping alone.
Individual Differences
• Borbely (1986) warns against the use of
generalisations about sleep patterns for different
age groups. He reports that Wilse Webb from the
University of Florida found marked differences
between different participants in his sleep
studies. Webb found consistent data from the
same participant on different nights but not
across participants, even when drawn from the
same age range. This suggests that sleep
patterns may be determined more by an
individual person’s constitution rather than a
cruder measure of age.
Operationalisation of sleep
• One difficulty with sleep research is to agree when sleep
occurs. Sleep onset is gradual and entails a predictable
sequence of events rather than a discrete event. Three
phases of sleep can be identified: Phase 1 – characterised by
calmness and immobility. Phase 2 – characterised by
decreased muscle tone and electroencephalograph changes
and phase 3 – characterised by an auditory threshold increase
and perceived sleep onset (Tyron, 2004) Many researchers
use EEG measures as the sole basis for defining sleep, but as
Allan Rechtschaffen (1994) states: EEG’s are reductionist
• “Physiological measures derive their value as indicators of
sleep from their correlations with the behavioural criteria,
not from any intrinsic ontological or explanatory superiority.
Any scientific definition of sleep that ignores the behaviours
by which sleep is generally known unnecessarily violates
common understanding and invites confusion”
Reductionist
It is argued that restricting the definition of sleep
to one measure (such as EEG) is akin to defining
intelligence as what an IQ test measures. As long
ago as 1963, Kleitman cited a dozen studies
showing discrepancies between behavioural and
EEG sleep criteria, and questioned EEG as the
sole basis for defining sleep. Although some of
these issues have been resolved through newer
criteria, the debate continues, particularly with
the use of new mobile sleep measure recording
devices, such as the wrist Actigraph, which,
although easier to use, have question marks
concerning their validity.
Cultural differences
(traditions)
• In Northern and Central Europe and North America, adults
tend to adopt a so-called monophasic pattern of sleep (that
is, they sleep for one long period during the night) and much
of the research outlined would be applicable to these
countries.
• However, in a significant number of countries (around the
Mediterranean, Central and South America), adults take naps
during the afternoon (Polyphasic). These siestas enable
people to avoid working in the hottest part of the afternoon.
Night-time sleep is thus delayed until later in the evening.
• Borbely (1986) reports that only 42% of Greeks adopt this
polyphasic sleeping pattern and that the practice of taking a
siesta is on the decrease.
• However, in China, the custom of an afternoon nap (called
xiu-xi) is still widely observed.
16 mark Essay
• Discuss life span changes in sleep (16m)
– Evaluation only. (Age related changes)
•
•
•
•
•
•
•
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Compare and contrast differences between age groups
REM changes with – brain dev
SWS34 changes – Age related decline – GH and immune syst.
Cultural differences: mono/polyphasic
Cultural differences: Teenagers
Objective measurements
Reporting difficulties
Individual differences
Under researched groups
Methodological problems
Reductionist
Describe and evaluate research and/or explanations
into the nature of sleep, an ultradian rhythm (24m)
AO1
Ultradian length
EEG, EOG, EMG’S
REM/nREM SWS
Brain activity in each stage
Stage and activity
Sleep deprivation studies
-Human sleep studies
-Animal sleep studies
Changes over a life time
(see Life span PP on uniservity)
What they teach us about sleep
AO2/3 (IDA)
Genetics
NT’s influence
Brian areas – case studies
Importance of psychology as a science
Objectivity (myths)
Artificiality
-Reductionist
Approach to study is reductionist
Universality – Evolutionary (ad hoc)
Individual differences
Case studies – bias
Fatal familial insomnia - genes
Ethics with humans
Ethics with Animals
Comparison studies
Cross cultural studies – mono/poly
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Life Span changes in Sleep