Sleep & D exam 1

Polysomnography (PSG)

• Overnight tracking of physiological channels:

  • 3 main parts

    • brain activity (EEG)

    • eye movements (EOG)

    • muscle movements (EMG)

  • more that may be added

    • nasel flow

    • respiratory effort

    • oxygen saturation

    • cardiac rate and rhythm

    • …and more

pros:

cons:

• lab is an unfamiliar, clinical environment; patients are hooked up to monitors & wires

• expensive

Electroencephalogram (EEG)

• dates to 1920s

• series of macroelectrodes placed across scalp

• shows relative (not absolute) brain activity, between 2 adjacent electrodes

EOG and EMG

Sleep onset (SOL)

time it takes to fall asleep

Sleep efficiency (SE)

total time asleep (TST) / the total time in bed

Wake after sleep onset (WASO)

amount of time awake after first sleep

Multiple sleep latency test (MSLT)

Sleepiness test

• given 4 or 5 nap opportunities every 2 hours

  • if patient takes an average of 5 or less mins to sleep = at risk for sleep disorder

  • if patient has quick entry into REM = likely narcolepsy

Maintenance of wakefulness test (MWT)

Sleepiness test

• told to stay awake in bed, in a dark room during the day

Actigraphy and wearables

• wristband measures ur movement

• the original focus was sleep/wake not includes heart rate, etc.

• Advantages:

  • discrete, forget its there, for research: able to track many people sleep at once, for ex, across regions

• Disadvantages:

  • hard to know how accurate it is, may work different for different people

  • maybe risk for causing or worsening “Orthosomnia“ - being obsessed with your sleep

Subjective measures of sleep

• Intake interviews: before sleep tests, questions like “how much sleep do you get per night”

• Sleep diaries: thing were doing for assignment now

• Self-report questionnaires: things we did for first assignment

CR 4 activity patterns

1. Diurnal- awake during day, sleep at night (humans)\

2. Nocturnal- sleep during day (owls)

3. Crepuscular- most active at dusk and dawn (foxes, deer)

4. Cathemeral- don’t fit in the other categories, unpredictable, active & sleep during day & night(lions)

Phase delay

sleep cycle is shifted later (like blue light keeping you awake)

Phase advance

sleep cycle is shifted earlier

Phase peak

top of sleep cycle

Phase nadir

bottom of sleep cycle

Early CR research- de Mairan (1729) - Study of mimosa pudica plant

• like sunflowers, this plant follows the patterns of the sun

• but found this was actually an internal process not really from the sun

Early CR research- Kleitman & Richardson (1938)- Mammoth cave experiment

• studying CR in isolation

• slept in cave with no light, or outside cues

• they started having a cycle of over 24 hours

• found that humans dont have exacly 24 hour internal cycle

Early CR research- Aschoff & Wever (1976)- Bunker experiments

• slept in bunkers with no light, or outside cues

• able to choose their own light/dark times, and sleep/wake times

• people went to bed later and later

• found we have an average of 24 hr. 11 min. cycle

Circadian Rhythm (“Process C”)

• Internal clock, roughly 24.2 hours

• promotes wake or sleep depending on the time

• synchronized with external cues

• Zeitgebers (“time givers“)

  • Light/ dark

  • Others (e.g. feeding times)

Physiology of CR “Process C"

• suprachiasmatic nucleus (SCN) as central pacemaker

• melatonin as dark signal for body

  • sleep onset

  • releases around 9pm for us

  • process of release is same for diurnal & nocturnal

• Pathway: Pineal gland —> SCN

Sleep pressure (“Process S“)

• homeostatic

• buildup of adenosine while awake

• inhibition of regions involved in arousal

• depleted during sleep

Two-process model (Borbély, 1982)

• interaction of Process C & Process S

• smaller gap between the two processes means a smaller desire for sleep

Influence of caffeine

• Antagonist for adenosine

  • adenosine continues to be produced and built up but has no where to go

  • caffeine fills the receptor sites so adenosine can’t

• Peak & Half-life

  • peak is about a half hour after consuming the caffeine

  • half-life is about 5-7 hours after consuming the caffeine

• Caffeine crash is because adenosine is still building up, so when the caffeine wears off, you notice all the built up sleepiness

• Individual differences-

  • more or less efficient enzymes

  • age- caffeine effects & lasts longer for old people than young people

Effects of artificial light on CR

• Blue light

  • eye —> thalamus —> SCN —> pineal gland —> melatonin

• Light hygiene- getting bright light during day & lowering light exposure at night

CR- Jet lag

• Eastbound- wont be tired for bed, no melatonin yet cause we think its earlier than is

• Westbound- will be tired before bed

• Going eastbound is harder to adjust to than westbound

  • people find it easier to stay up late than go to bed early

• Treatment:

  • east- phase advance

    • melatonin

    • bright light in morning

  • west- phase delay

    • light in evening

    • dark in morning

  • red-eye- hardest bc you leave one day and arrive the next

    • sleep on plane

    • stay awake through day 2

    • no naps

    • bright light

CR- Nightshift work

• Concerns

  • shift is inconsistent with light and dark

  • bright light from sun when you get out of shift may keep you awake

  • often revert to “normal“ schedule on days off

• Health concerns

  • world health org- classified shift work as a carcinogen in 2007

  • links with various health impacts

• Treatment

  • days off “compromise“ phase position, go to bed at 3am instead of 8am

  • melatonin, blackout curtains, white noise

  • limit light exposure when driving home

Chronotypes

• morningness vs. eveningness

• factors leading to which a person is

  • genetic

  • social

  • environment

  • developmental stage

    • young kids go to bed & wake up earlier than teens/young adults, then older adults revert back to earlier sleep & wake

  • personality differences

    • the big 5:

      • morning ppl high in- conscientiousness

      • evening ppl high in- extraversion, openness, risk-taking, sensation seeking

    • health

      • physical

        • morning- healthy behaviors

        • evening- diabetes, heart disease, cancer

      • psychological-

        • evening- depression, anxiety

Delayed sleep-wake phase disorder (DSWPD)

Consistent phase delay (fall asleep and wake up much later than most)

Advanced sleep-wake phase disorder (ASWPD)

Consistent phase advance (fall asleep and wake up much earlier than most)

Irregular sleep-wake rhythm disorder (ISWRD)

Sleep occurs in multiple bouts throughout the day and night

Non-24-hour sleep-wake rhythm disorder (N24SWRD)

“Free running disorder” – follow +24 hr. rhythm, mostly seen in blind people

Sleep stages- Stage 1 (N1)

• less than 10 minutes spent in this stage

  • spend the least amount of time in this stage, ab 2-5% of the night

• lightest sleep we have

• decreased breathing, muscle tone

• slow rolling eye movements

• hypogogic hallucinations- hearing sounds, feeling like ur falling

• hypnic jerks

• slight lowering of awareness

• may deny or be unaware of being in N1 (“no I wasn’t sleeping”)

Sleep stages- Stage 2 (N2)

• Body

  • no eye movement

  • decreasing muscle tone

  • metabolic activity

• Brain

  • mostly theta waves (moderate frequency)

  • k complexes: (“knock”)

  • occurs ab 1/min

• Sleep spindles

  • high frequency

  • occurs ab 2.5/min

  • may help maintain sleep

  • hippocampus —> memory cortex

Sleep stages- Stage 3 (N3)

• Body

  • decreased muscle tone, breathing rate, metabolic activity

  • hormone release (growth hormones)

• Brain

  • delta waves- low frequency

  • high amplitude

  • high synchronization

  • thalamus is turning down signals for environment to protect from waking

  • parasympathetic NS dominates

• Experience

  • hard to be woken up

  • confusion/ mental fog/ grogginess

  • dreaming occurs, less vivid and less common than in REM

  • parasomnias occur here

Sleep stages- Rapid eye movement (REM)

• Body

  • rapid eye movement, eyes are synchronized

  • atonia- no muscle tone

  • blood flow in brain similar to waking

  • irregular breathing, heart rate

  • tumescence (genital arousal/ bood engorgement)

• Brain

  • no delta waves, instead “sawtooth waves“ like alpha, beta

  • phasic vs. tonic

    • phasic: Rem, irregularities, twitches, no k complexes/sleep spindles, thalamus & amygdala are highly active, less activity in prefrontal cortex

    • tonic: no REM, less irregularity

• Experience

  • vivid dreaming, most frequent

  • almost as hard to be woken up as in N3

Brain waves during sleep

• Gamma waves - during high alertness and deep focus - 30-100Hz

• Beta waves - while awake - 13-30Hz

• Alpha waves - while relaxed or sleepy - 8-13Hz

• Theta waves - during stage 1 & 2, light sleep - 4-8Hz

• Delta waves - during stage 3, deep sleep - 1-4Hz

• to remember the order:

  • Great Big Apples Taste Delicious