Summary
Summary sleep & sleep disorders (PSY3349/IPN3349)
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Task 1What is sleep (stages and what do they look like)?
Sleep architecture
Based on frequency (Hz, number of waves per second)
and amplitude (size of a wave) > defined by electrical
activity using EEG.
Awake: beta activity (13-30Hz).
o Arousal/ High muscle tension
Drowsy/relaxation: Alpha activity (8-12Hz).
o Often precedes falling asleep when eyes are
closed
NREM
o Stage 1 (N1): lightest > easy to be awakened,
least likely to perceive having been asleep.
Hippocampal theta rhythms (4-7 Hz): Low
amplitude, high frequency.
Decreased arousal and reduction of consciousness.
EOG: slow rolling eye movements
5-10 min
o Stage 2 (N2): Intermediate > theta
K-complexes (sharp spikes > single delta wave) > suppress external stimuli not
seen as dangerous, memory consolidation, forerunner of delta waves.
Sleep spindles (short bursts of high frequency > 12-16hz) > important for memory
consolidation.
Interaction thalamus and cortex
o Stage 3 (N3 + N4) or SWS: deepest sleep stage > Delta waves (0.5-2 Hz): Low
frequency, high amplitude
Thalamus/cortical
Most restful stage since metabolic activity of the brain is the lowest
Muscle tension becomes less and less with progression of sleep stages
When sleep-deprived brain will first catch up on this sleep stage the next night
REM: Beta and theta waves > mixed frequency > Low voltage: random, fast with sawtooth
waves.
o Resembles waking activity.
o Vivid dreaming, emotional memory, REM (EOG), muscle atonia (EMG), irregular
breathing and poor thermoregulation.
o Oxygen consumption in the brain is very high, sometimes even higher than in
wakefulness
o Difference to wakefulness is that EMG shows almost no activity in REM
First sleep cycle: begins with N1 and proceeds through the sleep stages until the first REM
episode with an average of 70 minutes. Faster is associated with depression and
narcolepsy.
The rest of the night is spent cycling between NREM and REM sleep in a similar fashion >
subsequent cycles of roughly 90 -120 minutes. Brief awakenings during sleep stage
transitions are normal.
Cycle repeats 4/5 times on average per night.
What ways can we measure sleep? (not a main topic)
PSG (Polysomnography): data on electrical brain activities + muscle tone > golden
standard for measuring sleep.
o EEG (cortical activity), EOG (eye movements), EMG (muscle tension)
o Create a hypnogram from the data: measures sleep duration and continuity and
additional to the sleep stages you can look at:
SOL: sleep onset latency (min) => How long does it take to fall asleep
Number of awakenings
WASO: Wake after sleep onset => How many minutes is the person awake after
sleep onset
TIB: Time in bed => how much time does the person spend in bed
, TST: total sleep time (TIB – (SOL + WASO)
SE: Sleep efficiency % of (TST/TIB)
Actigraphy: Wrist movement > no info sleep stages.
Subjective measures: sleep diaries.
Daytime sleepiness: Multiple Sleep Latency Test (MSLT) > Fall asleep as fast as you can &
the Maintenance of Wakefulness Test (MWT) > Stay awake for as long as you can.
Measures of sleep architecture:
o REM latency in minutes
o Sleep stages in percent
How many hours of sleep is normal? What is the relation between age and sleep?
TST: 7-7.5 hours, WASO: +- 20 minutes, Sleep efficiency: 85-95 %
REM: maximal in newborn infants > rapid decline until age 3-4 yrs
SWS: maximal in young children > rapid decline in adolescence (especially in men).
WASO: maximal in elderly > rare in young children
National Sleep Foundation’s updated sleep duration recommendations: final report
– Hirshkowitz
Newborns: 0-3 months Teenagers: 14-17 years
14/17h sleep duration for overall health. 8-10h
Subjective data instead of objective data. Convincing and weaker evidence.
Longer than 19h may limit environmental Short sleep duration > decreased
interaction and may impede cognitive alertness, car accidents, depressed
and/or emotional development. mood, obesity, poor health, and low
May not apply to first days. academic performance.
Sleep duration may vary on maturational Interventional research shows that
changes. delaying school-start times
approximately 1 hour later increases
Infants: 4-11 months students’ sleep duration and decreases
12-15h daytime sleepiness.
Based of weaker scientific evidence the
opinions/experience of the panel Young adult: 18-25 years
members. 7-9h
Rapid maturational changes > sleep Both convincing scientific evidence and
durations can vary based on age. weaker scientific evidence.
Longer sleep durations needed for Teenagers represent a mixed group for
different components of health. sleep patterns due to differences related
Limited evidence suggests an association to responsibilities, school, work, and
between short sleep duration and social life.
abnormal physical growth and obesity. Short sleep duration > increased fatigue,
Long sleep durations could limit an decreased psychomotor performance,
infant’s environmental interaction that accidents, poor physical and
might impede cognitive development, psychological health, and low academic
emotional development, or both. performance.
Healthy sleep patterns enhance
Toddlers: 1-2 years adjustment and performance in college
11-14h. years,
Some convincing evidence, weaker Early bedtimes, wake times, and napping
scientific evidence, and the Panel correlate with the high academic
members’ own experience and/or performance.
opinion. Finally, extended sleep leads to
Association between short sleep duration, substantial improvements in daytime
obesity, hyperactivity-impulsivity, and alertness, reaction time, and mood.
lower cognitive functioning.
Slightly longer sleep durations might Adults: 26-64 years
benefit toddlers’ emotional health. 7-9h
Long sleep duration could interfere with Both convincing and weaker scientific
toddlers’ exploration of their physical and evidence.
social environment and thereby impede Slightly shorter sleep durations might be
motor, cognitive, and social sufficient for emotional health.
, development. Restricted sleep time particularly affects
45- to 54-year-olds, the age range when
Preschooler: 3-5 years time at work usually reaches its
10-13h maximum in the life span.
Slightly shorter sleep durations might be Sleep deprivation’s adverse effect on
sufficient for physical and emotional multitasking performance, weight
health > both convincing and weaker regulation, job safety, mental health,
scientific evidence. sugar regulation, blood pressure, and
Evidence showing that preschoolers who cardiovascular health was noted,
slept less than 9 hours per night have particularly with nighttime sleep
greater odds of being obese than those deprivation during the workweek.
sleeping 10 or more was considered.
Older adult: ≥ 65 years
School-age: 6-13 years 7-8h
9-11h Both convincing and weaker scientific
Scientific evidence, some strong and evidence.
some weak. Reduced total sleep duration and sleep
Research indicating associations between fragmentation.
short sleep in school-aged children and Less employment-related responsibilities
lower cognitive functioning and poorer and obligatory sleep schedule demands &
academic performance. older adults often nap.
A postpubertal adolescent typically Sleep need changes little compared with
sleeps less than a younger prepubertal younger adults.
school-aged child. Older adults sleeping 6-9 hours have
Increase sleep duration > cognitive and better cognitive functioning, lower rates
academic performance improves. of mental and physical illnesses, and
enhanced quality of life compared with
shorter or longer sleep durations.
However, long sleep duration (≥9-10
hours) in older adults is associated with
morbidity (eg, hypertension, diabetes,
atrial fibrillation, poor general health) and
mortality.
Daytime napping is perceived as
common. However, older adults report
more daytime sleepiness than younger
adults. Overall, the literature contains
conflicting reports concerning napping’s
association with morbidity in older adults
(possibly because they have more health
issues).
Discussion
Sleep restriction may predispose a person to adverse health conditions. By contrast,
atypically increased sleep duration may suggest compensation for diminished sleep depth
and/or quality.
Individuals with daily sleep duration far outside of the recommended range need serious
assessment.
Limitations
o Few reports include objective measures.
o Total bedtime rather than sleep time is
considered.
o Pathology not considered.
Correlates of sleep quality in midlife and
beyond: a machine learning analysis –
Kaplan
Introduction
, Studies using polysomnography (PSG) confirm that age-related changes in sleep
predispose older individuals to increased fragmentation and wakefulness at night.
Despite the deterioration in objective sleep quality, subjective sleep quality reports appear
to plateau or even improve with advancing age.
Aim: qEEG characteristics in predicting subjective sleep quality alongside demographic and
clinical factors in midlife and beyond.
Methods
3172 included participants above 39.
Polysomnography (PSG): unattended
o Total sleep time, wake after sleep onset (WASO), percentage of time spent in each
sleep stage, latency to rapid eye movement (REM) sleep, the number of sleep to wake
shifts per hour, the number of deep (N3) to lighter (N1/N2) stage shifts per hour, and
sleep efficiency. Apneaehypopnea index also used.
o EEG
Morning sleep diary: quality of sleep > high is better quality > sleep depth and sleep
restfulness.
Participants reported, in hours, their habitual sleep duration on weekdays and weekends,
which were collapsed to a weighted average reflecting habitual sleep duration across the
week. Daytime sleepiness was assessed using the Epworth Sleepiness Scale.
Results
Model variables had relatively low predictive value for sleep depth and restfulness.
Although of low predictive value, sleep efficiency, age, WASO, and habitual sleep duration
were the top predictors for both aspects of sleep quality.
The OLS model predicting sleep depth retained three variables with significant p values:
sleep efficiency, age, and habitual sleep duration.
There were four variables predicting sleep restfulness: WASO, age, race, and habitual
sleep duration.
Sample into quartiles of age.
o Traditional PSG metrics were most important in explaining subjective sleep quality
across models. However, the relative contributions of various predictors of subjective
sleep quality did not appear to change as a function of age.
o Objective sleep efficiency was among the most important of the predictor variables.
o The relationship suggests that, at any given level of objective sleep efficiency,
individuals in the older two cohorts will rate their subjective sleep quality as
progressively better relative to the younger two cohorts.
Standard metrics derived from PSG, including qEEG, contribute little to explaining
subjective sleep quality in middle-aged to older adults. The objective correlates of
subjective sleep quality do not appear to systematically change with age despite a change
in the relationship between subjective sleep quality and objective sleep efficiency.
Discussion
However, we should note that although we found a strong sex effect in our older adult
sample, sex was not determined to be an important predictor of subjective sleep quality in
this midlife sample.
Divergence between subjective and objective measures.
o As individuals age, the relationship between sleep efficiency and both sleep depth and
sleep restfulness changes such that for the same level of objective sleep efficiency,
there is a greater sleep quality subjectively reported.
o While an individual in the first age quartile (aged 39-55 years) with 85% sleep
efficiency would rate themselves approximately 2.9 on the sleep depth scale, an
individual in the fourth quartile (aged 73-90 years) with the same 85% sleep efficiency
would rate themselves approximately 3.2 on this scale, about a 10% improvement.
Note: data are crossectional and not longitudinal.
Limitations
o Restricted number of variables in the models to a subset of the standard metrics
derivable from both PSg and qEEg.
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